Где хранятся теневые копии windows server 2008 r2 - Доктор Windows

Задался я тут после одного инцидента как сделать быстрый бекап удаленного файла или папки с сетевой папки на сервере и заодно посмотреть кто это сделал.

Ну вопрос, кто это сделал нашли сразу через аудит (это рассмотрит в другой статье)

А вот вопрос, быстрого восстановления файла меня очень сильно заинтересовал. Я по своему обычаю на основной файловой помойке делаю бекап с помощью Acronis и дифференцированного бекапа (это будет отдельная статья)

В итоге решил на файловую помойку прикрутить еще один бекап и тут встал вопрос, либо сделать ее зеркалируемый и что бы один или несколько раз в неделю происходила синхронизация диска например с помощью штатной утилиты robocopy (и ее в одной из статей опишу) либо сделать на теневом копировании. Данный способ после совещания с коллегами был выбран как основой в виду его основного плюса с версиями файла и быстрого восстановления. Сказано сделано.

Поднимаем теневое копирование на Windows Server Standart 2008 R2

Для начала надо включить теневое копирование на диске, для это проделываем следующую операцию:

1) Пуск->Мой компьютер -> «щелкаем правой кнопкой» -> Управление Компьютером ->Общие Папки -> «щелкаем правой кнопкой» -> Все задачи -> Настроить теневые копии

2) Теперь выбираем диск на котором будем делать Теневые копии и нажимаем Параметры. Тут мы задаем место где будут хранится теневые копии и расписание их создания.

3) Далее выбираем диск на котором включаем теневое копирование, в моем случае это будет диск D и сразу при включении он начнем создавать первую копию диска.
тут же будут отражены все копии по времени когда либо создаваемые теневым копированием, которые можно удалять, либо Восстановить, но это я крайне не советую потому как он тогда затрет выбранной копией все что находится в сетевой папке.

Для работы с теневыми копиями и восстановлением файлов будет пользоваться по другому.

Ситуация 1

Допустим у нас теневая копия снимается один раз в день (в конце дня). И Вас просят восстановить файл который нечаянно был перезаписан (название файлов одно и тоже)

наши действия:

1) «щелкаем правой кнопкой» на файле который надо восстановить -> Свойство -> Предыдущая версия
2) выбираем ту версию которая нам нужна и восстаналиваем

Ситуация 2

К Вам вбегаю манагеры и кричат что кто то удалил их файл или папку с важными документами, а шеф уже ее ждет. 🙂

Действуем так:

1) «щелкаем правой кнопкой» на папке в которой лежал удаленный файл или папка -> Свойство -> Предыдущая версия

2) смотрим последние версии нашего бекапа и восстаналиваем файл или папку

3) ждем от коллег кофе или шоколадку))))

Видео по Теневому копированию (Shadow Copy)

nibbl

Я отец двух сыновей, ITишник, предприниматель и просто человек который любит делиться полезной информацией с другими людьми на такие темы как: Windows, Unix, Linux, Web, SEO и многое другое!

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Собственно вопросик следующий. Имеется домен, в нём сервера на windows 2008R2 и т.д., и соот-но настроен бэкап стандартным средством (backup фичей) системного раздела вместе с систем стейтом на др. раздел (volume). На разделах Shadow Copy (или правильнее
будет сказать shadow copyprev versions for shared folders?) не включены:

http://img526.imageshack.us/img526/817/vss.gif

Собственно при бэкапе используется VSS и, насколько я понимаю, он создаёт shadow copy тех разделов которые должны быть включены в бэкап по любому — что бы потом с них снять бэкап. После бэкапа (который идёт на отдельный раздел) в нём ес-но появляется соот-я
папочка WindowsImageBackup содержащая бэкап и т.д. Однако после бэкапа судя по выводу утилит vssadminDiskshadow также в системе остаётся ещё и shadow copy раздела(ов), в частности:

PS> vssadmin list shadows
vssadmin 1.1 — Volume Shadow Copy Service administrative command-line tool
(C) Copyright 2001-2005 Microsoft Corp.

Contents of shadow copy set ID: {db43b2db-3569-5dd4-ee1d-3bd6ce6c3455}
   Contained 1 shadow copies at creation time: 11.06.2010 17:39:23
      Shadow Copy ID: {ec245937-4555-4975-8092-dcd0336c2433}
         Original Volume: (D:)\?Volume{1d7a0f57-1e67-11df-ba97-22330e226322}
         Shadow Copy Volume: \?GLOBALROOTDeviceHarddiskVolumeShadowCopy1
         Originating Machine: srv1.domain.ru
         Service Machine: srv1.domain.ru
         Provider: ‘Microsoft Software Shadow Copy provider 1.0’
         Type: DataVolumeRollback
         Attributes: Persistent, No auto release, No writers, Differential

Собственно вопрос — почему она осталась? (afaik атрибут Persistent указывает именно на то, что данная теневая копия тома именно постоянная?)

+ на рисунке выше почему тогда все диски в состоянии disable находятся для теневых копий если они всё равно появляются? (или там имеется ввиду именно для shared folders, а теневые копии как таковые включены по любому?)

PS может заодно есть линк на подробное описание полей выводимых утилитами vssadminDiskshadow а то то что на мсдн-е лежит слишком кратко…

Изменен тип

27 сентября 2010 г. 7:12
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Содержание

1 Как восстановить удалённые файлы из теневых копий Windows
2 Где хранятся теневые копии Windows
3 Работа с теневыми копиями посредством shadowcopyview
4 Работа с теневыми копиями из командной строки

Здравствуйте, друзья! Вот и добрался я в очередной раз до карандаша и бумаги. Точнее до ноутбука и виртуальной машины. Сегодня хочу рассказать о таком безусловно интересном и полезном явлении, как предыдущие версии файлов или теневые копии Windows.

Продемонстрируем на практике работу с теневыми копиями.

Вот у нас имеется рабочий стол Windows. На нём две папки screen и zip, которые мы будем удалять и восстанавливать. Третья папка – ShadowExplorer – программа, при помощи которой я буду работать с теневыми копиями. Программу я прикладываю здесь, берите и пользуйтесь!
Итак, поскольку предыдущие версии файлов (теневые копии) используют контрольные точки восстановления, нам потребуется создать как минимум одну точку. Для этого перейдём в свойства системы, на вкладку “Защита системы”. Нам важно, чтобы в параметрах защиты стоял режим “Включено”, в настройках также можно задать резервируемый объём диска в процентном соотношении под эти контрольные точки, а также моментально создать точку восстановления (кнопка “Создать”)

Нажимаем “Создать”, вводим имя контрольной точки:
Процесс создания контрольной точки (делее – КТ) занимает некоторое время.

Теперь, когда процесс создания КТ завершён, в свойствах папок на вкладке “Предыдущие версии” видны данные о копии, дате. Это означает, что в зарезервированном месте на диске у нас имеется “теневая копия” данного файлового объекта.Теперь, что мы делаем? Просто напросто удаляем ненужные (пока) нам объекты, то есть два этих каталога. Теперь представим, что случилось это не вполне осознанно и мы пожалели о содеянном. Захотели папки вернуть!

Конечно, можно прибегнуть к программам восстановления данных, тем более, что объект удалили весьма недавно и есть вероятность его восстановить. Но что, если это не так? Что, если программы восстановления данных не дали нужного результата?

На помощь приходят данные из “теневых копий“. Запустим программу ShadowExplorer. Мы увидим в главном окне выпадающие списки – в первом – диск, на котором создаются теневые копии, во втором – дата создания снимка системы.

Так как снимок системы, как и логический раздел у нас в единственном экземпляре, то откроются именно нужные нам данные. В дереве каталогов развернём нужную директорию и увидим, что наши, ныне удалённые каталоги там ещё остались! Кликнем правой кнопкой на нужном каталоге и нажмём “Export”. И вот, объект восстановлен! Конечно это не универсальный способ, но тем не менее, вполне жизнеспособный и полезный.

Где хранятся теневые копии Windows

Теневые копии Windows хранятся в каталоге “System Volume Information“, в файлах с именами, выглядящими как {GUID}{GUID2}, где {GUID} – идентификатор копии, {GUID2} – идентификатор раздела.

Работа с теневыми копиями посредством shadowcopyview

От Nirsoft есть отличный инструмент, позволяющий довольно удобно работать с теневыми копиями. Имя этой программке ShadowCopyView. Её я также прикладываю к статье, при желании можете скачать актуальную версию с сайта разработчиков – она бесплатная.

В главном окне отображаются теневые копии (в верхней части), ниже – их содержимое. Также есть пункт контекстного меню “Copy Selected Files To…“, позволяющий вытащить из теневой копии содержимое.

Работа с теневыми копиями из командной строки

Но что делать, если под рукой не оказалось каких-либо инструментов? Не беда, можно подмонтировать том теневой копии посредством командной строки и открыть теневую копию в качестве каталога в проводнике.

Первым делом, нам нужно получить список теневых копий:

> vssadmin list shadows

Все теневые копии будут выведены в подобном виде. Здесь нас интересует дата создания и поле “Том теневой копии”. Скопируем эту строку и создадим символическую ссылку на этот каталог:

> mklink /D C:old \?GLOBALROOTDeviceHarddiskVolumeShadowCopy1

Внимание! Слеш в конце обязателен, на скрине я снял без слеша и не получилось войти в каталог. Команда mklink создаёт ссылку C:old на каталог (ключ /D) резервной копии.

Посмотрим, как это выглядит в проводнике:

Войдём в каталог и увидим привычную картину – состояние файловой системы на момент снятия резервной копии.

Но это вовсе не значит, что у нас на диске теперь записано в 2 раза больше информации. Эта информация помечена как свободная, но она не будет перезаписываться до тех пор, пока не исчерпается свободное место, отделённое на этапе настройки службы резервного копирования. Помните, мы там указывали, какой процент диска выделять под резервные копии. Только после того, как всё оставшееся место будет исчерпано, будут затираться теневые копии изменённых файлов.

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Наиболее распространенная проблема с которой сталкиваются пользователи и администраторы файловых серверов — это случайное удаление или перезапись файлов. Бороться с этим явлением весьма сложно, технические средства здесь не помогут, а административные часто оказываются неэффективными. Очень часто сотрудники сами случайно перезаписывают нужные файлы. Что делать? Ответ прост — настраивать теневое копирование общих папок.

Научиться настраивать MikroTik с нуля или систематизировать уже имеющиеся знания можно на углубленном курсе по администрированию MikroTik. Автор курса, сертифицированный тренер MikroTik Дмитрий Скоромнов, лично проверяет лабораторные работы и контролирует прогресс каждого своего студента. В три раза больше информации, чем в вендорской программе MTCNA, более 20 часов практики и доступ навсегда.

Теневое копирование — специальный механизм, позволяющий делать копии файлов соответствующее определенному моменту времени, даже если они открыты или заблокированы системой. Теневые копии позволяют просматривать содержимое общих папок по состоянию на тот или иной момент времени в прошлом.

Теневые копии могут быть использованы для восстановления случайно удаленных и случайно перезаписанных файлов, а также позволяет сравнить несколько версий одного файла. Следует помнить, что теневые копии не могут служить заменой резервному копированию в силу ряда ограничений и особенностей о которых мы поговорим ниже.

Теневое копирование поддерживают серверные ОС начиная с Windows Server 2003, клиентское ПО для работы с теневыми копиями доступно начиная с Windows XP SP2.

При использовании теневых копий следует учитывать следующие ограничения:

При превышении лимита выделенного дискового пространства старые теневые копии будут удалены без возможности восстановления.
На одном томе может быть не более 64 теневых копий для каждого файла.
Теневое копирование включается на уровне тома, т.е. нельзя выбрать общие папки и файлы для которых будет или не будет выполнятся теневое копирование.
На компьютерах с двумя ОС при загрузке более старой системы или при подключении тома к другому ПК теневые копии могут быть повреждены.

Перед тем, как настраивать теневое копирование, следует продумать расписание. Для этого нужно проанализировать активность пользователей и критичность данных, найдя компромисс между частотой создания теневых копий и промежутком времени который должно охватывать теневое копирование. При этом следует отталкиваться от того, потерю какого промежутка рабочего времени можно считать допустимым, после чего рассчитать за какой промежуток времени будет достигнут предел, составляющий 64 копии. Не рекомендуется делать теневые копии чаще чем раз в час. Также продумайте расписание таким образом, чтобы копии делались только в рабочее время.

Для включения теневых копий перейдите в оснастку Управление компьютером в меню Администрирование.

В левой части окна найдите пункт Общие папки и, щелкнув правой кнопкой мыши, выберите Все задачи — Настроить теневые копии.

В открывшемся окне выберите том, на котором вы будете включать теневое копирование для общих папок и нажмите Включить, первая теневая копия будет создана немедленно.

Затем нажмите на кнопку Параметры и укажите размер дискового пространства, выделяемый для хранения теневых копий.

Следующим шагом задайте расписание.

Теперь самое время проверить работу теневых копий в действии. В обучающих целях мы установили небольшой промежуток между созданием теневых копий и провели несколько типовых действий с файлами в общей папке.

Самая распространенная и труднорешаемая проблема — файл перезаписали.

Открываем свойства файла, переходим на закладку Предыдущие версии и выбираем одну из доступных теневых копий (в нашем случае только одна).

Мы можем открыть, восстановить или скопировать файл. Для начала просто откроем.

Убедившись, что перед нами необходимая версия файла, мы можем ее восстановить или скопировать, если нам нужны оба варианта файлов.

Для восстановления удаленных файлов откройте свойства папки и выберите одну из ее теневых копий, затем вы можете просмотреть содержащиеся в ней файлы и восстановить нужные. Помните, что из теневой копии файлы можно открыть только на чтение.

Как видим, теневое копирование дает пользователям и администратору богатые возможности по работе предыдущими версиями файлов и папок. Данная технология, в сочетании с правильно настроенным резервным копированием, позволяет обеспечить высокую доступность данных и свести риск их потери к разумному минимуму.

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description	title	ms.date	author	manager	ms.author	ms.topic
Learn more about: Volume Shadow Copy Service	Volume Shadow Copy Service	12/06/2022	JasonGerend	elizapo	jgerend	article

Volume Shadow Copy Service

Applies to: Windows Server 2022, Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, and Windows Server 2008 R2, Windows Server 2008, Windows 10, Windows 8.1, Windows 8, Windows 7

Backing up and restoring critical business data can be very complex due to the following issues:

The data usually needs to be backed up while the applications that produce the data are still running. This means that some of the data files might be open or they might be in an inconsistent state.
If the data set is large, it can be difficult to back up all of it at one time.

Correctly performing backup and restore operations requires close coordination between the backup applications, the line-of-business applications that are being backed up, and the storage management hardware and software. The Volume Shadow Copy Service (VSS), which was introduced in Windows Server® 2003, facilitates the conversation between these components to allow them to work better together. When all the components support VSS, you can use them to back up your application data without taking the applications offline.

VSS coordinates the actions that are required to create a consistent shadow copy (also known as a snapshot or a point-in-time copy) of the data that is to be backed up. The shadow copy can be used as-is, or it can be used in scenarios such as the following:

You want to back up application data and system state information, including archiving data to another hard disk drive, to tape, or to other removable media.
You are data mining.
You are performing disk-to-disk backups.
You need a fast recovery from data loss by restoring data to the original Logical Unit Number (LUN) or to an entirely new LUN that replaces an original LUN that failed.

Windows features and applications that use VSS include the following:

Windows Server Backup (https://go.microsoft.com/fwlink/?LinkId=180891)
Shadow Copies of Shared Folders (https://go.microsoft.com/fwlink/?LinkId=142874)
System Center Data Protection Manager (https://go.microsoft.com/fwlink/?LinkId=180892)
System Restore (https://support.microsoft.com/windows/use-system-restore-a5ae3ed9-07c4-fd56-45ee-096777ecd14e)

How Volume Shadow Copy Service Works

A complete VSS solution requires all of the following basic parts:

VSS service Part of the Windows operating system that ensures the other components can communicate with each other properly and work together.

VSS requester The software that requests the actual creation of shadow copies (or other high-level operations like importing or deleting them). Typically, this is the backup application. The Windows Server Backup utility and the System Center Data Protection Manager application are VSS requesters. Non-Microsoft® VSS requesters include nearly all backup software that runs on Windows.

VSS writer The component that guarantees we have a consistent data set to back up. This is typically provided as part of a line-of-business application, such as SQL Server® or Exchange Server. VSS writers for various Windows components, such as the registry, are included with the Windows operating system. Non-Microsoft VSS writers are included with many applications for Windows that need to guarantee data consistency during back up.

VSS provider The component that creates and maintains the shadow copies. This can occur in the software or in the hardware. The Windows operating system includes a VSS provider that uses copy-on-write. If you use a storage area network (SAN), it is important that you install the VSS hardware provider for the SAN, if one is provided. A hardware provider offloads the task of creating and maintaining a shadow copy from the host operating system.

The following diagram illustrates how the VSS service coordinates with requesters, writers, and providers to create a shadow copy of a volume.

Figure 1 Architectural diagram of Volume Shadow Copy Service

How a Shadow Copy Is Created

This section puts the various roles of the requester, writer, and provider into context by listing the steps that need to be taken to create a shadow copy. The following diagram shows how the Volume Shadow Copy Service controls the overall coordination of the requester, writer, and provider.

Figure 2 Shadow copy creation process

To create a shadow copy, the requester, writer, and provider perform the following actions:

The requester asks the Volume Shadow Copy Service to enumerate the writers, gather the writer metadata, and prepare for shadow copy creation.
Each writer creates an XML description of the components and data stores that need to be backed up and provides it to the Volume Shadow Copy Service. The writer also defines a restore method, which is used for all components. The Volume Shadow Copy Service provides the writer’s description to the requester, which selects the components that will be backed up.
The Volume Shadow Copy Service notifies all the writers to prepare their data for making a shadow copy.
Each writer prepares the data as appropriate, such as completing all open transactions, rolling transaction logs, and flushing caches. When the data is ready to be shadow-copied, the writer notifies the Volume Shadow Copy Service.
The Volume Shadow Copy Service tells the writers to temporarily freeze application write I/O requests (read I/O requests are still possible) for the few seconds that are required to create the shadow copy of the volume or volumes. The application freeze is not allowed to take longer than 60 seconds. The Volume Shadow Copy Service flushes the file system buffers and then freezes the file system, which ensures that the file system metadata is recorded correctly and the data to be shadow-copied is written in a consistent order.
The Volume Shadow Copy Service tells the provider to create the shadow copy. The shadow copy creation period lasts no more than 10 seconds, during which all write I/O requests to the file system remain frozen.
The Volume Shadow Copy Service releases file system write I/O requests.
VSS tells the writers to thaw application write I/O requests. At this point applications are free to resume writing data to the disk that is being shadow-copied.

[!NOTE]
The shadow copy creation can be aborted if the writers are kept in the freeze state for longer than 60 seconds or if the providers take longer than 10 seconds to commit the shadow copy.

The requester can retry the process (go back to step 1) or notify the administrator to retry at a later time.
If the shadow copy is successfully created, the Volume Shadow Copy Service returns the location information for the shadow copy to the requester. In some cases, the shadow copy can be temporarily made available as a read-write volume so that VSS and one or more applications can alter the contents of the shadow copy before the shadow copy is finished. After VSS and the applications make their alterations, the shadow copy is made read-only. This phase is called Auto-recovery, and it is used to undo any file-system or application transactions on the shadow copy volume that were not completed before the shadow copy was created.

How the Provider Creates a Shadow Copy

A hardware or software shadow copy provider uses one of the following methods for creating a shadow copy:

Complete copy This method makes a complete copy (called a «full copy» or «clone») of the original volume at a given point in time. This copy is read-only.

Copy-on-write This method does not copy the original volume. Instead, it makes a differential copy by copying all changes (completed write I/O requests) that are made to the volume after a given point in time.

Redirect-on-write This method does not copy the original volume, and it does not make any changes to the original volume after a given point in time. Instead, it makes a differential copy by redirecting all changes to a different volume.

Complete copy

A complete copy is usually created by making a «split mirror» as follows:

The original volume and the shadow copy volume are a mirrored volume set.
The shadow copy volume is separated from the original volume. This breaks the mirror connection.

After the mirror connection is broken, the original volume and the shadow copy volume are independent. The original volume continues to accept all changes (write I/O requests), while the shadow copy volume remains an exact read-only copy of the original data at the time of the break.

Copy-on-write method

In the copy-on-write method, when a change to the original volume occurs (but before the write I/O request is completed), each block to be modified is read and then written to the volume’s shadow copy storage area (also called its «diff area»). The shadow copy storage area can be on the same volume or a different volume. This preserves a copy of the data block on the original volume before the change overwrites it.

Time	Source data (status and data)	Shadow copy (status and data)
T0	Original data: 1 2 3 4 5	No copy: —
T1	Data changed in cache: 3 to 3′	Shadow copy created (differences only): 3
T2	Original data overwritten: 1 2 3′ 4 5	Differences and index stored on shadow copy: 3

Table 1 The copy-on-write method of creating shadow copies

The copy-on-write method is a quick method for creating a shadow copy, because it copies only data that is changed. The copied blocks in the diff area can be combined with the changed data on the original volume to restore the volume to its state before any of the changes were made. If there are many changes, the copy-on-write method can become expensive.

Redirect-on-write method

In the redirect-on-write method, whenever the original volume receives a change (write I/O request), the change is not applied to the original volume. Instead, the change is written to another volume’s shadow copy storage area.

Time	Source data (status and data)	Shadow copy (status and data)
T0	Original data: 1 2 3 4 5	No copy: —
T1	Data changed in cache: 3 to 3′	Shadow copy created (differences only): 3′
T2	Original data unchanged: 1 2 3 4 5	Differences and index stored on shadow copy: 3′

Table 2 The redirect-on-write method of creating shadow copies

Like the copy-on-write method, the redirect-on-write method is a quick method for creating a shadow copy, because it copies only changes to the data. The copied blocks in the diff area can be combined with the unchanged data on the original volume to create a complete, up-to-date copy of the data. If there are many read I/O requests, the redirect-on-write method can become expensive.

Shadow Copy Providers

There are two types of shadow copy providers: hardware-based providers and software-based providers. There is also a system provider, which is a software provider that is built in to the Windows operating system.

Hardware-based providers

Hardware-based shadow copy providers act as an interface between the Volume Shadow Copy Service and the hardware level by working in conjunction with a hardware storage adapter or controller. The work of creating and maintaining the shadow copy is performed by the storage array.

Hardware providers always take the shadow copy of an entire LUN, but the Volume Shadow Copy Service only exposes the shadow copy of the volume or volumes that were requested.

A hardware-based shadow copy provider makes use of the Volume Shadow Copy Service functionality that defines the point in time, allows data synchronization, manages the shadow copy, and provides a common interface with backup applications. However, the Volume Shadow Copy Service does not specify the underlying mechanism by which the hardware-based provider produces and maintains shadow copies.

Software-based providers

Software-based shadow copy providers typically intercept and process read and write I/O requests in a software layer between the file system and the volume manager software.

These providers are implemented as a user-mode DLL component and at least one kernel-mode device driver, typically a storage filter driver. Unlike hardware-based providers, software-based providers create shadow copies at the software level, not the hardware level.

A software-based shadow copy provider must maintain a «point-in-time» view of a volume by having access to a data set that can be used to re-create volume status before the shadow copy creation time. An example is the copy-on-write technique of the system provider. However, the Volume Shadow Copy Service places no restrictions on what technique the software-based providers use to create and maintain shadow copies.

A software provider is applicable to a wider range of storage platforms than a hardware-based provider, and it should work with basic disks or logical volumes equally well. (A logical volume is a volume that is created by combining free space from two or more disks.) In contrast to hardware shadow copies, software providers consume operating system resources to maintain the shadow copy.

For more information about basic disks, see What Are Basic Disks and Volumes?.

System provider

One shadow copy provider, the system provider, is supplied in the Windows operating system. Although a default provider is supplied in Windows, other vendors are free to supply implementations that are optimized for their storage hardware and software applications.

To maintain the «point-in-time» view of a volume that is contained in a shadow copy, the system provider uses a copy-on-write technique. Copies of the blocks on volume that have been modified since the beginning of the shadow copy creation are stored in a shadow copy storage area.

The system provider can expose the production volume, which can be written to and read from normally. When the shadow copy is needed, it logically applies the differences to data on the production volume to expose the complete shadow copy.

For the system provider, the shadow copy storage area must be on an NTFS volume. The volume to be shadow copied does not need to be an NTFS volume, but at least one volume mounted on the system must be an NTFS volume.

The component files that make up the system provider are swprv.dll and volsnap.sys.

In-Box VSS Writers

The Windows operating system includes a set of VSS writers that are responsible for enumerating the data that is required by various Windows features.

For more information about these writers, see In-Box VSS Writers.

How Shadow Copies Are Used

In addition to backing up application data and system state information, shadow copies can be used for a number of purposes, including the following:

Restoring LUNs (LUN resynchronization and LUN swapping)
Restoring individual files (Shadow Copies for Shared Folders)
Data mining by using transportable shadow copies

Restoring LUNs (LUN resynchronization and LUN swapping)

In Windows Server 2008 R2 and Windows 7, VSS requesters can use a hardware shadow copy provider feature called LUN resynchronization (or «LUN resync»). This is a fast-recovery scheme that allows an application administrator to restore data from a shadow copy to the original LUN or to a new LUN.

The shadow copy can be a full clone or a differential shadow copy. In either case, at the end of the resync operation, the destination LUN will have the same contents as the shadow copy LUN. During the resync operation, the array performs a block-level copy from the shadow copy to the destination LUN.

[!NOTE]
The shadow copy must be a transportable hardware shadow copy.

Most arrays allow production I/O operations to resume shortly after the resync operation begins. While the resync operation is in progress, read requests are redirected to the shadow copy LUN, and write requests to the destination LUN. This allows arrays to recover very large data sets and resume normal operations in several seconds.

LUN resynchronization is different from LUN swapping. A LUN swap is a fast recovery scenario that VSS has supported since Windows Server 2003 SP1. In a LUN swap, the shadow copy is imported and then converted into a read-write volume. The conversion is an irreversible operation, and the volume and underlying LUN cannot be controlled with the VSS APIs after that. The following list describes how LUN resynchronization compares with LUN swapping:

In LUN resynchronization, the shadow copy is not altered, so it can be used several times. In LUN swapping, the shadow copy can be used only once for a recovery. For the most safety-conscious administrators, this is important. When LUN resynchronization is used, the requester can retry the entire restore operation if something goes wrong the first time.
At the end of a LUN swap, the shadow copy LUN is used for production I/O requests. For this reason, the shadow copy LUN must use the same quality of storage as the original production LUN to ensure that performance is not impacted after the recovery operation. If LUN resynchronization is used instead, the hardware provider can maintain the shadow copy on storage that is less expensive than production-quality storage.
If the destination LUN is unusable and needs to be recreated, LUN swapping may be more economical because it doesn’t require a destination LUN.

[!WARNING]
All of the operations listed are LUN-level operations. If you attempt to recover a specific volume by using LUN resynchronization, you are unwittingly going to revert all the other volumes that are sharing the LUN.

Restoring individual files (Shadow Copies for Shared Folders)

Shadow Copies for Shared Folders uses the Volume Shadow Copy Service to provide point-in-time copies of files that are located on a shared network resource, such as a file server. With Shadow Copies for Shared Folders, users can quickly recover deleted or changed files that are stored on the network. Because they can do so without administrator assistance, Shadow Copies for Shared Folders can increase productivity and reduce administrative costs.

For more information about Shadow Copies for Shared Folders, see Shadow Copies for Shared Folders (https://go.microsoft.com/fwlink/?LinkId=180898) on TechNet.

Data mining by using transportable shadow copies

With a hardware provider that is designed for use with the Volume Shadow Copy Service, you can create transportable shadow copies that can be imported onto servers within the same subsystem (for example, a SAN). These shadow copies can be used to seed a production or test installation with read-only data for data mining.

With the Volume Shadow Copy Service and a storage array with a hardware provider that is designed for use with the Volume Shadow Copy Service, it is possible to create a shadow copy of the source data volume on one server, and then import the shadow copy onto another server (or back to the same server). This process is accomplished in a few minutes, regardless of the size of the data. The transport process is accomplished through a series of steps that use a shadow copy requester (a storage-management application) that supports transportable shadow copies.

To transport a shadow copy

Create a transportable shadow copy of the source data on a server.
Import the shadow copy to a server that is connected to the SAN (you can import to a different server or the same server).
The data is now ready to be used.

Figure 3 Shadow copy creation and transport between two servers

[!NOTE]
A transportable shadow copy that is created on Windows Server 2003 cannot be imported onto a server that is running Windows Server 2008 or Windows Server 2008 R2. A transportable shadow copy that was created on Windows Server 2008 or Windows Server 2008 R2 cannot be imported onto a server that is running Windows Server 2003. However, a shadow copy that is created on Windows Server 2008 can be imported onto a server that is running Windows Server 2008 R2 and vice versa.

Shadow copies are read-only. If you want to convert a shadow copy to a read/write LUN, you can use a Virtual Disk Service-based storage-management application (including some requesters) in addition to the Volume Shadow Copy Service. By using this application, you can remove the shadow copy from Volume Shadow Copy Service management and convert it to a read/write LUN.

Volume Shadow Copy Service transport is an advanced solution on computers running Windows Server 2003 Enterprise Edition, Windows Server 2003 Datacenter Edition, Windows Server 2008, or Windows Server 2008 R2. It works only if there is a hardware provider on the storage array. Shadow copy transport can be used for a number of purposes, including tape backups, data mining, and testing.

Frequently Asked Questions

This FAQ answers questions about Volume Shadow Copy Service (VSS) for system administrators. For information about VSS application programming interfaces, see Volume Shadow Copy Service (https://go.microsoft.com/fwlink/?LinkId=180899) in the Windows Developer Center Library.

When was Volume Shadow Copy Service introduced? On which Windows operating system versions is it available?

VSS was introduced in Windows XP. It is available on Windows XP, Windows Server 2003, Windows Vista®, Windows Server 2008, Windows 7, and Windows Server 2008 R2.

What is the difference between a shadow copy and a backup?

In the case of a hard disk drive backup, the shadow copy created is also the backup. Data can be copied off the shadow copy for a restore or the shadow copy can be used for a fast recovery scenario—for example, LUN resynchronization or LUN swapping.

When data is copied from the shadow copy to tape or other removable media, the content that is stored on the media constitutes the backup. The shadow copy itself can be deleted after the data is copied from it.

What is the largest size volume that Volume Shadow Copy Service supports?

Volume Shadow Copy Service supports a volume size of up to 64 TB.

I made a backup on Windows Server 2008. Can I restore it on Windows Server 2008 R2?

It depends on the backup software that you used. Most backup programs support this scenario for data but not for system state backups.

Shadow copies that are created on either of these versions of Windows can be used on the other.

I made a backup on Windows Server 2003. Can I restore it on Windows Server 2008?

It depends on the backup software you used. If you create a shadow copy on Windows Server 2003, you cannot use it on Windows Server 2008. Also, if you create a shadow copy on Windows Server 2008, you cannot restore it on Windows Server 2003.

How can I disable VSS?

It is possible to disable the Volume Shadow Copy Service by using the Microsoft Management Console. However, you should not do this. Disabling VSS adversely affects any software you use that depends on it, such as System Restore and Windows Server Backup.

For more information, see the following Microsoft TechNet Web sites:

System Restore (https://go.microsoft.com/fwlink/?LinkID=157113)
Windows Server Backup (https://go.microsoft.com/fwlink/?LinkID=180891)

Can I exclude files from a shadow copy to save space?

VSS is designed to create shadow copies of entire volumes. Temporary files, such as paging files, are automatically omitted from shadow copies to save space.

To exclude specific files from shadow copies, use the following registry key: FilesNotToSnapshot.

[!NOTE]
The FilesNotToSnapshot registry key is intended to be used only by applications. Users who attempt to use it will encounter limitations such as the following:

It cannot delete files from a shadow copy that was created on a Windows Server by using the Previous Versions feature.

It cannot delete files from shadow copies for shared folders.

It can delete files from a shadow copy that was created by using the Diskshadow utility, but it cannot delete files from a shadow copy that was created by using the Vssadmin utility.

Files are deleted from a shadow copy on a best-effort basis. This means that they are not guaranteed to be deleted.

For more information, see Excluding Files from Shadow Copies (https://go.microsoft.com/fwlink/?LinkId=180904) on MSDN.

My non-Microsoft backup program failed with a VSS error. What can I do?

Check the product support section of the Web site of the company that created the backup program. There may be a product update that you can download and install to fix the problem. If not, contact the company’s product support department.

System administrators can use the VSS troubleshooting information on the following Microsoft TechNet Library Web site to gather diagnostic information about VSS-related issues.

For more information, see Volume Shadow Copy Service (https://go.microsoft.com/fwlink/?LinkId=180905) on TechNet.

What is the «diff area»?

The shadow copy storage area (or «diff area») is the location where the data for the shadow copy that is created by the system software provider is stored.

Where is the diff area located?

The diff area can be located on any local volume. However, it must be located on an NTFS volume that has enough space to store it.

How is the diff area location determined?

The following criteria are evaluated, in this order, to determine the diff area location:

If a volume already has an existing shadow copy, that location is used.
If there is a preconfigured manual association between the original volume and the shadow copy volume location, then that location is used.
If the previous two criteria do not provide a location, the shadow copy service chooses a location based on available free space. If more than one volume is being shadow copied, the shadow copy service creates a list of possible snapshot locations based on the size of free space, in descending order. The number of locations provided is equal to the number of volumes being shadow copied.
If the volume being shadow copied is one of the possible locations, then a local association is created. Otherwise an association with the volume with the most available space is created.

Can VSS create shadow copies of non-NTFS volumes?

Yes. However, persistent shadow copies can be made only for NTFS volumes. In addition, at least one volume mounted on the system must be an NTFS volume.

What’s the maximum number of shadow copies I can create at one time?

The maximum number of shadow copied volumes in a single shadow copy set is 64. Note that this is not the same as the number of shadow copies.

What’s the maximum number of software shadow copies created by the system provider that I can maintain for a volume?

The max number is of software shadow copies for each volume is 512. However, by default you can only maintain 64 shadow copies that are used by the Shadow Copies of Shared Folders feature. To change the limit for the Shadow Copies of Shared Folders feature, use the following registry key: MaxShadowCopies.

How can I control the space that is used for shadow copy storage space?

Type the vssadmin resize shadowstorage command.

For more information, see Vssadmin resize shadowstorage (https://go.microsoft.com/fwlink/?LinkId=180906) on TechNet.

What happens when I run out of space?

Shadow copies for the volume are deleted, beginning with the oldest shadow copy.

Volume Shadow Copy Service Tools

The Windows operating system provides the following tools for working with VSS:

DiskShadow (https://go.microsoft.com/fwlink/?LinkId=180907)
VssAdmin (https://go.microsoft.com/fwlink/?LinkId=84008)

DiskShadow

DiskShadow is a VSS requester that you can use to manage all the hardware and software snapshots that you can have on a system. DiskShadow includes commands such as the following:

list: Lists VSS writers, VSS providers, and shadow copies
create: Creates a new shadow copy
import: Imports a transportable shadow copy
expose: Exposes a persistent shadow copy (as a drive letter, for example)
revert: Reverts a volume back to a specified shadow copy

This tool is intended for use by IT professionals, but developers might also find it useful when testing a VSS writer or VSS provider.

DiskShadow is available only on Windows Server operating systems. It is not available on Windows client operating systems.

VssAdmin

VssAdmin is used to create, delete, and list information about shadow copies. It can also be used to resize the shadow copy storage area («diff area»).

VssAdmin includes commands such as the following:

create shadow: Creates a new shadow copy
delete shadows: Deletes shadow copies
list providers: Lists all registered VSS providers
list writers: Lists all subscribed VSS writers
resize shadowstorage: Changes the maximum size of the shadow copy storage area

VssAdmin can only be used to administer shadow copies that are created by the system software provider.

VssAdmin is available on Windows client and Windows Server operating system versions.

Volume Shadow Copy Service Registry Keys

The following registry keys are available for use with VSS:

VssAccessControl
MaxShadowCopies
MinDiffAreaFileSize

VssAccessControl

This key is used to specify which users have access to shadow copies.

For more information, see the following entries on the MSDN Web site:

Security Considerations for Writers (https://go.microsoft.com/fwlink/?LinkId=157739)
Security Considerations for Requesters (https://go.microsoft.com/fwlink/?LinkId=180908)

MaxShadowCopies

This key specifies the maximum number of client-accessible shadow copies that can be stored on each volume of the computer. Client-accessible shadow copies are used by Shadow Copies for Shared Folders.

For more information, see the following entry on the MSDN Web site:

MaxShadowCopies under Registry Keys for Backup and Restore (https://go.microsoft.com/fwlink/?LinkId=180909)

MinDiffAreaFileSize

This key specifies the minimum initial size, in MB, of the shadow copy storage area.

For more information, see the following entry on the MSDN Web site:

MinDiffAreaFileSize under Registry Keys for Backup and Restore (https://go.microsoft.com/fwlink/?LinkId=180910)

Supported Operating System Versions

The following table lists the minimum supported operating system versions for VSS features.

VSS feature

Minimum supported client

Minimum supported server

LUN resynchronization

None supported

Windows Server 2008 R2

FilesNotToSnapshot registry key

Windows Vista

Windows Server 2008

Transportable shadow copies

None supported

Windows Server 2003 with SP1

Hardware shadow copies

None supported

Windows Server 2003

Previous versions of Windows Server

Windows Vista

Windows Server 2003

Fast recovery using LUN swap

None supported

Windows Server 2003 with SP1

Multiple imports of hardware shadow copies

Note
This is the ability to import a shadow copy more than once. Only one import operation can be performed at a time.

None supported

Windows Server 2008

Shadow Copies for Shared Folders

None supported

Windows Server 2003

Transportable auto-recovered shadow copies

None supported

Windows Server 2008

Concurrent backup sessions (up to 64)

Windows XP

Windows Server 2003

Single restore session concurrent with backups

Windows Vista

Windows Server 2003 with SP2

Up to 8 restore sessions concurrent with backups

Windows 7

Windows Server 2003 R2

Additional References

Volume Shadow Copy Service in Windows Developer Center

Источник

description	title	ms.date	author	manager	ms.author	ms.topic
Learn more about: Volume Shadow Copy Service	Volume Shadow Copy Service	12/06/2022	JasonGerend	elizapo	jgerend	article

Volume Shadow Copy Service

Applies to: Windows Server 2022, Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, and Windows Server 2008 R2, Windows Server 2008, Windows 10, Windows 8.1, Windows 8, Windows 7

Backing up and restoring critical business data can be very complex due to the following issues:

The data usually needs to be backed up while the applications that produce the data are still running. This means that some of the data files might be open or they might be in an inconsistent state.
If the data set is large, it can be difficult to back up all of it at one time.

You want to back up application data and system state information, including archiving data to another hard disk drive, to tape, or to other removable media.
You are data mining.
You are performing disk-to-disk backups.
You need a fast recovery from data loss by restoring data to the original Logical Unit Number (LUN) or to an entirely new LUN that replaces an original LUN that failed.

Windows features and applications that use VSS include the following:

Windows Server Backup (https://go.microsoft.com/fwlink/?LinkId=180891)
Shadow Copies of Shared Folders (https://go.microsoft.com/fwlink/?LinkId=142874)
System Center Data Protection Manager (https://go.microsoft.com/fwlink/?LinkId=180892)
System Restore (https://support.microsoft.com/windows/use-system-restore-a5ae3ed9-07c4-fd56-45ee-096777ecd14e)

How Volume Shadow Copy Service Works

A complete VSS solution requires all of the following basic parts:

VSS service Part of the Windows operating system that ensures the other components can communicate with each other properly and work together.

The following diagram illustrates how the VSS service coordinates with requesters, writers, and providers to create a shadow copy of a volume.

Figure 1 Architectural diagram of Volume Shadow Copy Service

How a Shadow Copy Is Created

Figure 2 Shadow copy creation process

To create a shadow copy, the requester, writer, and provider perform the following actions:

The requester asks the Volume Shadow Copy Service to enumerate the writers, gather the writer metadata, and prepare for shadow copy creation.
Each writer creates an XML description of the components and data stores that need to be backed up and provides it to the Volume Shadow Copy Service. The writer also defines a restore method, which is used for all components. The Volume Shadow Copy Service provides the writer’s description to the requester, which selects the components that will be backed up.
The Volume Shadow Copy Service notifies all the writers to prepare their data for making a shadow copy.
Each writer prepares the data as appropriate, such as completing all open transactions, rolling transaction logs, and flushing caches. When the data is ready to be shadow-copied, the writer notifies the Volume Shadow Copy Service.
The Volume Shadow Copy Service tells the writers to temporarily freeze application write I/O requests (read I/O requests are still possible) for the few seconds that are required to create the shadow copy of the volume or volumes. The application freeze is not allowed to take longer than 60 seconds. The Volume Shadow Copy Service flushes the file system buffers and then freezes the file system, which ensures that the file system metadata is recorded correctly and the data to be shadow-copied is written in a consistent order.
The Volume Shadow Copy Service tells the provider to create the shadow copy. The shadow copy creation period lasts no more than 10 seconds, during which all write I/O requests to the file system remain frozen.
The Volume Shadow Copy Service releases file system write I/O requests.
VSS tells the writers to thaw application write I/O requests. At this point applications are free to resume writing data to the disk that is being shadow-copied.

[!NOTE]
The shadow copy creation can be aborted if the writers are kept in the freeze state for longer than 60 seconds or if the providers take longer than 10 seconds to commit the shadow copy.

The requester can retry the process (go back to step 1) or notify the administrator to retry at a later time.
If the shadow copy is successfully created, the Volume Shadow Copy Service returns the location information for the shadow copy to the requester. In some cases, the shadow copy can be temporarily made available as a read-write volume so that VSS and one or more applications can alter the contents of the shadow copy before the shadow copy is finished. After VSS and the applications make their alterations, the shadow copy is made read-only. This phase is called Auto-recovery, and it is used to undo any file-system or application transactions on the shadow copy volume that were not completed before the shadow copy was created.

How the Provider Creates a Shadow Copy

A hardware or software shadow copy provider uses one of the following methods for creating a shadow copy:

Complete copy This method makes a complete copy (called a «full copy» or «clone») of the original volume at a given point in time. This copy is read-only.

Complete copy

A complete copy is usually created by making a «split mirror» as follows:

The original volume and the shadow copy volume are a mirrored volume set.
The shadow copy volume is separated from the original volume. This breaks the mirror connection.

Copy-on-write method

Time	Source data (status and data)	Shadow copy (status and data)
T0	Original data: 1 2 3 4 5	No copy: —
T1	Data changed in cache: 3 to 3′	Shadow copy created (differences only): 3
T2	Original data overwritten: 1 2 3′ 4 5	Differences and index stored on shadow copy: 3

Table 1 The copy-on-write method of creating shadow copies

Redirect-on-write method

Time	Source data (status and data)	Shadow copy (status and data)
T0	Original data: 1 2 3 4 5	No copy: —
T1	Data changed in cache: 3 to 3′	Shadow copy created (differences only): 3′
T2	Original data unchanged: 1 2 3 4 5	Differences and index stored on shadow copy: 3′

Table 2 The redirect-on-write method of creating shadow copies

Shadow Copy Providers

Hardware-based providers

Hardware providers always take the shadow copy of an entire LUN, but the Volume Shadow Copy Service only exposes the shadow copy of the volume or volumes that were requested.

Software-based providers

Software-based shadow copy providers typically intercept and process read and write I/O requests in a software layer between the file system and the volume manager software.

For more information about basic disks, see What Are Basic Disks and Volumes?.

System provider

The component files that make up the system provider are swprv.dll and volsnap.sys.

In-Box VSS Writers

The Windows operating system includes a set of VSS writers that are responsible for enumerating the data that is required by various Windows features.

For more information about these writers, see In-Box VSS Writers.

How Shadow Copies Are Used

In addition to backing up application data and system state information, shadow copies can be used for a number of purposes, including the following:

Restoring LUNs (LUN resynchronization and LUN swapping)
Restoring individual files (Shadow Copies for Shared Folders)
Data mining by using transportable shadow copies

Restoring LUNs (LUN resynchronization and LUN swapping)

[!NOTE]
The shadow copy must be a transportable hardware shadow copy.

In LUN resynchronization, the shadow copy is not altered, so it can be used several times. In LUN swapping, the shadow copy can be used only once for a recovery. For the most safety-conscious administrators, this is important. When LUN resynchronization is used, the requester can retry the entire restore operation if something goes wrong the first time.
At the end of a LUN swap, the shadow copy LUN is used for production I/O requests. For this reason, the shadow copy LUN must use the same quality of storage as the original production LUN to ensure that performance is not impacted after the recovery operation. If LUN resynchronization is used instead, the hardware provider can maintain the shadow copy on storage that is less expensive than production-quality storage.
If the destination LUN is unusable and needs to be recreated, LUN swapping may be more economical because it doesn’t require a destination LUN.

[!WARNING]
All of the operations listed are LUN-level operations. If you attempt to recover a specific volume by using LUN resynchronization, you are unwittingly going to revert all the other volumes that are sharing the LUN.

Restoring individual files (Shadow Copies for Shared Folders)

For more information about Shadow Copies for Shared Folders, see Shadow Copies for Shared Folders (https://go.microsoft.com/fwlink/?LinkId=180898) on TechNet.

Data mining by using transportable shadow copies

To transport a shadow copy

Create a transportable shadow copy of the source data on a server.
Import the shadow copy to a server that is connected to the SAN (you can import to a different server or the same server).
The data is now ready to be used.

Figure 3 Shadow copy creation and transport between two servers

[!NOTE]
A transportable shadow copy that is created on Windows Server 2003 cannot be imported onto a server that is running Windows Server 2008 or Windows Server 2008 R2. A transportable shadow copy that was created on Windows Server 2008 or Windows Server 2008 R2 cannot be imported onto a server that is running Windows Server 2003. However, a shadow copy that is created on Windows Server 2008 can be imported onto a server that is running Windows Server 2008 R2 and vice versa.

Frequently Asked Questions

When was Volume Shadow Copy Service introduced? On which Windows operating system versions is it available?

VSS was introduced in Windows XP. It is available on Windows XP, Windows Server 2003, Windows Vista®, Windows Server 2008, Windows 7, and Windows Server 2008 R2.

What is the difference between a shadow copy and a backup?

What is the largest size volume that Volume Shadow Copy Service supports?

Volume Shadow Copy Service supports a volume size of up to 64 TB.

I made a backup on Windows Server 2008. Can I restore it on Windows Server 2008 R2?

It depends on the backup software that you used. Most backup programs support this scenario for data but not for system state backups.

Shadow copies that are created on either of these versions of Windows can be used on the other.

I made a backup on Windows Server 2003. Can I restore it on Windows Server 2008?

How can I disable VSS?

For more information, see the following Microsoft TechNet Web sites:

System Restore (https://go.microsoft.com/fwlink/?LinkID=157113)
Windows Server Backup (https://go.microsoft.com/fwlink/?LinkID=180891)

Can I exclude files from a shadow copy to save space?

VSS is designed to create shadow copies of entire volumes. Temporary files, such as paging files, are automatically omitted from shadow copies to save space.

To exclude specific files from shadow copies, use the following registry key: FilesNotToSnapshot.

[!NOTE]
The FilesNotToSnapshot registry key is intended to be used only by applications. Users who attempt to use it will encounter limitations such as the following:

It cannot delete files from a shadow copy that was created on a Windows Server by using the Previous Versions feature.

It cannot delete files from shadow copies for shared folders.

It can delete files from a shadow copy that was created by using the Diskshadow utility, but it cannot delete files from a shadow copy that was created by using the Vssadmin utility.

Files are deleted from a shadow copy on a best-effort basis. This means that they are not guaranteed to be deleted.

For more information, see Excluding Files from Shadow Copies (https://go.microsoft.com/fwlink/?LinkId=180904) on MSDN.

My non-Microsoft backup program failed with a VSS error. What can I do?

System administrators can use the VSS troubleshooting information on the following Microsoft TechNet Library Web site to gather diagnostic information about VSS-related issues.

For more information, see Volume Shadow Copy Service (https://go.microsoft.com/fwlink/?LinkId=180905) on TechNet.

What is the «diff area»?

The shadow copy storage area (or «diff area») is the location where the data for the shadow copy that is created by the system software provider is stored.

Where is the diff area located?

The diff area can be located on any local volume. However, it must be located on an NTFS volume that has enough space to store it.

How is the diff area location determined?

The following criteria are evaluated, in this order, to determine the diff area location:

If a volume already has an existing shadow copy, that location is used.
If there is a preconfigured manual association between the original volume and the shadow copy volume location, then that location is used.
If the previous two criteria do not provide a location, the shadow copy service chooses a location based on available free space. If more than one volume is being shadow copied, the shadow copy service creates a list of possible snapshot locations based on the size of free space, in descending order. The number of locations provided is equal to the number of volumes being shadow copied.
If the volume being shadow copied is one of the possible locations, then a local association is created. Otherwise an association with the volume with the most available space is created.

Can VSS create shadow copies of non-NTFS volumes?

Yes. However, persistent shadow copies can be made only for NTFS volumes. In addition, at least one volume mounted on the system must be an NTFS volume.

What’s the maximum number of shadow copies I can create at one time?

The maximum number of shadow copied volumes in a single shadow copy set is 64. Note that this is not the same as the number of shadow copies.

What’s the maximum number of software shadow copies created by the system provider that I can maintain for a volume?

How can I control the space that is used for shadow copy storage space?

Type the vssadmin resize shadowstorage command.

For more information, see Vssadmin resize shadowstorage (https://go.microsoft.com/fwlink/?LinkId=180906) on TechNet.

What happens when I run out of space?

Shadow copies for the volume are deleted, beginning with the oldest shadow copy.

Volume Shadow Copy Service Tools

The Windows operating system provides the following tools for working with VSS:

DiskShadow (https://go.microsoft.com/fwlink/?LinkId=180907)
VssAdmin (https://go.microsoft.com/fwlink/?LinkId=84008)

DiskShadow

DiskShadow is a VSS requester that you can use to manage all the hardware and software snapshots that you can have on a system. DiskShadow includes commands such as the following:

list: Lists VSS writers, VSS providers, and shadow copies
create: Creates a new shadow copy
import: Imports a transportable shadow copy
expose: Exposes a persistent shadow copy (as a drive letter, for example)
revert: Reverts a volume back to a specified shadow copy

This tool is intended for use by IT professionals, but developers might also find it useful when testing a VSS writer or VSS provider.

DiskShadow is available only on Windows Server operating systems. It is not available on Windows client operating systems.

VssAdmin

VssAdmin is used to create, delete, and list information about shadow copies. It can also be used to resize the shadow copy storage area («diff area»).

VssAdmin includes commands such as the following:

create shadow: Creates a new shadow copy
delete shadows: Deletes shadow copies
list providers: Lists all registered VSS providers
list writers: Lists all subscribed VSS writers
resize shadowstorage: Changes the maximum size of the shadow copy storage area

VssAdmin can only be used to administer shadow copies that are created by the system software provider.

VssAdmin is available on Windows client and Windows Server operating system versions.

Volume Shadow Copy Service Registry Keys

The following registry keys are available for use with VSS:

VssAccessControl
MaxShadowCopies
MinDiffAreaFileSize

VssAccessControl

This key is used to specify which users have access to shadow copies.

For more information, see the following entries on the MSDN Web site:

Security Considerations for Writers (https://go.microsoft.com/fwlink/?LinkId=157739)
Security Considerations for Requesters (https://go.microsoft.com/fwlink/?LinkId=180908)

MaxShadowCopies

For more information, see the following entry on the MSDN Web site:

MaxShadowCopies under Registry Keys for Backup and Restore (https://go.microsoft.com/fwlink/?LinkId=180909)

MinDiffAreaFileSize

This key specifies the minimum initial size, in MB, of the shadow copy storage area.

For more information, see the following entry on the MSDN Web site:

MinDiffAreaFileSize under Registry Keys for Backup and Restore (https://go.microsoft.com/fwlink/?LinkId=180910)

Supported Operating System Versions

The following table lists the minimum supported operating system versions for VSS features.

VSS feature

Minimum supported client

Minimum supported server

LUN resynchronization

None supported

Windows Server 2008 R2

FilesNotToSnapshot registry key

Windows Vista

Windows Server 2008

Transportable shadow copies

None supported

Windows Server 2003 with SP1

Hardware shadow copies

None supported

Windows Server 2003

Previous versions of Windows Server

Windows Vista

Windows Server 2003

Fast recovery using LUN swap

None supported

Windows Server 2003 with SP1

Multiple imports of hardware shadow copies

Note
This is the ability to import a shadow copy more than once. Only one import operation can be performed at a time.

None supported

Windows Server 2008

Shadow Copies for Shared Folders

None supported

Windows Server 2003

Transportable auto-recovered shadow copies

None supported

Windows Server 2008

Concurrent backup sessions (up to 64)

Windows XP

Windows Server 2003

Single restore session concurrent with backups

Windows Vista

Windows Server 2003 with SP2

Up to 8 restore sessions concurrent with backups

Windows 7

Windows Server 2003 R2

Additional References

Volume Shadow Copy Service in Windows Developer Center

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