This article answers following questions related to Windows Server Backup in Windows Server 2008 and Windows Server 2008 R2:

Q1. How does Windows Server Backup store backups and maintain backup versions?
Q2. How do I query backup stored versions on a backup storage location?
Q3. How do I delete non system state backups created using Windows Server Backup?
Q4. How do I delete system state backups created using Windows Server Backup?

Overview

• Windows Server Backup is the built-in backup solution in Windows Server 2008 and Windows Server 2008 R2. Using Windows Server Backup, an administrator can schedule periodic backups of a server and also create backups on demand. For details on using Windows Server Backup, please see the Installed Help for Windows Server 2008 (http://technet.microsoft.com/en-us/library/cc770757(WS.10).aspx) and for Windows Server 2008 R2 (http://technet.microsoft.com/en-us/library/cc770757.aspx).
• Windows Server Backup in Windows Server 2008 allows administrators to back up entire volumes. More flexibility is available in Windows Server 2008 R2 where administrators can pick and choose individual files and folders to be included in a backup. The technology used by Windows Server Backup to perform a backup differs based on the nature of the backup:
  • If you back up an entire volume, Windows Server Backup creates a block-level backup that reads directly from the volume by passing the file system.
  • If you back up just specific files and folders, Windows Server Backup reads individual files going through the file system.
• Windows Server Backup stores backups at the following path: <BackupStorageLocation>WindowsImageBackup<ComputerName>. A back up operation performs following steps:

1. Windows Server Backup reads data from source volumes and then creates a .vhd file per source volume on the backup storage location and writes the backup metadata.
2. Windows Server Backup stores backup versions in volume shadow copies. After the data write is complete, Windows Server Backup creates a shadow copy of the volume where the backup is stored using Volume Shadow Copy Service (VSS). This shadow copy retains the state of the storage volume as a “backup version” or “point-in-time” of the backup and must restore using this backup version. VSS is the underlying Microsoft technology required for maintaining backup versions. (For more information about VSS, see http://technet.microsoft.com/en-us/library/cc785914.aspx.)
3. After creating the shadow copy, Windows Server Backup updates the backup catalog which is stored on both the system volume of the server that is being backed up and the backup storage folder with the following information:
   • The backup time − The local system time of the server when the backup operation started.
   • The shadow copy identifier (Shadow Copy ID) − Used by Windows Server Backup to associate the backup version to the correct shadow copy.
   • Version identifier − Used by Windows Server Backup to uniquely identify a backup version. Users using command line tools (Wbadmin and the Windows PowerShell cmdlets for Windows Server Backup) will specify the version identifier as a parameter to the command to work with a backup version.

• If the backup storage location is full, Windows Server Backup automatically deletes the oldest backup version to make space for the current backup. Since each backup is stored inside a shadow copy, deleting a backup version is accomplished by simply deleting the corresponding shadow copy. However, space for a system state backup in Windows Server 2008 is not automatically managed by Windows Server Backup. See the section “How to Delete System State Backups” below for managing system state backups in Windows Server 2008.
• Windows Server Backup can store only one backup version on a network share (remote shared folder). You can store backups from multiple computers to a network share. A backup from a computer to a network share will be saved at: \<RemoteServer><SharedFolderPath>WindowsImageBackup<ComputerBackedUp>. To delete the backup on network share, you need to delete the <ComputerBackedUp> directory from network share.
• Windows Server Backup uses the .vhd format for writing backups. The current virtual hard disk specification limits the size of a virtual hard disk to be 2040 GB, which can fit a volume of size 2040 GB – 2 MB, (i.e., 2088958 MB). Windows Server Backup in Windows Server 2008 also limits the maximum source volume size to be 2088958 MB. In Windows Server 2008 R2, if you are not backing up a full volume and, instead, creating a backup of selected files/folders, your source volume size can be more than 2088958 MB, provided your actual data size is less than equal to 2088958 MB. If you are creating a full volume backup, the maximum source volume size limit continues to be 2088958 MB.

How to Query Backup Versions

To see the backup versions present in a particular computer, use the Wbadmin get versions command. Note that, to use the Wbadmin command, you must be a member of the Administrators group or Backup Operators group and must open an elevated instance Cmd.exe (click Start, right-click Command Prompt, and then click Run as administrator). For detailed Wbadmin command documentation, see: http://technet.microsoft.com/en-us/library/cc754015.aspx.

Sample output of Wbadmin get versions command:

wbadmin 1.0 – Backup command-line tool

(C) Copyright 2004 Microsoft Corp.

Backup time: 3/12/2009 10:55 AM

Backup target: Fixed Disk labeled New Volume(I:)

Version identifier: 03/12/2009-05:25

Can recover: Volume(s), File(s)

Snapshot ID: {f5e946da-5cc7-44c3-a747-9f1079e639b0}

Snapshot ID in the above output is new in Windows Server 2008 R2. Snapshot ID is same as Shadow Copy ID. It corresponds to a specific backup version and can be used to delete that backup version.

To view all backup versions on a particular backup storage location, type:

Wbadmin get versions -backupTarget:<BackupStorageLocation:>

For example, if you want to view all the backup versions on the backup storage location K:, type:

Wbadmin get versions –backupTarget:K:

In the output of Wbadmin get versions command, Backup time is the local system time and Version Identifier is the GMT time at the time the backup was created. If you change your system time zone, the value for Backup time will also change. Note that Version Identifier is a unique identifier for a given backup version and remains constant for a backup.

How to Delete Non-System State Backups

Windows Server Backup deletes a backup by just deleting the corresponding shadow copy and updating the backup catalog. You can perform the same steps manually to delete backups on demand. However, the backup catalog update cannot be done manually and it will happen instead during the next backup. In short, to delete a backup version manually, you need to delete the corresponding shadow copy from the backup storage location.

To delete a shadow copy, follow these general steps:

1. Identify the backup version you want to delete by querying the backup versions on your backup storage location.
2. Determine the shadow copy ID of the version you want to delete.
3. Delete the shadow copy.

Identify the backup version:

To list all the shadow copies on a volume, use the Vssadmin command. (For the complete syntax for Vssadmin, see: http://technet.microsoft.com/en-us/library/cc754968(WS.10).aspx.) The following command line lists all shadow copies on a specified backup storage location:

Vssadmin list shadows /for=<BackupTarget>

For example, to list the shadow copies on the location Y, type:

Vssadmin list shadows /for=Y:

Determine the shadow copy ID:

On Windows Server 2008 R2, the shadow copy ID is same as Snapshot ID given in the output of querying backups. On Windows Server 2008, you can find your backup’s shadow copy ID by looking at output of Vssadmin list shadows /for=<Backup Target>. Match the shadow copy creation time with your backup’s Backup time value.

Delete the Shadow Copy for the specific Shadow Copy ID:

1. To open a command prompt with elevated privileges, click Start, right-click Command Prompt, and then click Run as administrator.

Microsoft SyncToy

SyncToy 是由 微软 推出的一款免费的文件夹同步工具。虽然名字中有一个 Toy，但是大家可千万不要误以为它的功能弱爆了。实际上，我感觉这款软件还真是摆脱了微软大多数软件给人复杂和臃肿的印象，通过很简单的操作便能够完成复杂的操作，免去了大量重复的手动复制、移动操作。

SyncToy 支持三种同步模式：

• synchronize ：在这个模式下，SyncToy会使得两个文件夹完全一致，无论在哪一个文件夹中操作，对应的操作相当于都在另一个文件夹中执行了一次。（也就是我们所说的“同步”）。
• echo：echo模式的效果是，使得在左边文件夹中新增加的和被改变的内容会被备份到右边的文件夹中。在左侧被重命名的文件以及被删除了的文件，将也会在右侧的文件夹中删除。（这种模式与synchronize 很像，差别就在于这里只会从左边同步到右边，右边的操作对左边的文件夹无效~）。
• Contribute ：也就是我们常说的“增量备份”，相当于在echo的基础上，把所有的删除操作都屏蔽掉了，只要在左边文件夹中存在过的文件都会在右侧文件夹中存在。

相信上面这三种模式已经能够满足大多数人的需求了。对于 Microsoft SyncToy，一句话：简单+实用。

FreeFileSync

一听 FreeFileSync 这个名字就知道这又是一款免费的文件同步软件了（并且也是开源的哦）。而且这款软件也非常绿色，虽然需要下载安装包，但是在安装的时候可以选择便携模式安装。程序运行之后，（虽然界面有些丑陋……）选择两个文件夹，首先进行的是比较操作，可以非常直观地看出文件夹之间的差异（可以 选择根据 文件内容 来判定而不是文件名）。而且我倒是觉得通过文件内容判定不同的话，这个软件还可以用来对两个不同版本的项目中，哪些代码文件做了修改之类的进行对比分析。

除了 SyncToy 中提到的那三种同步的模式以外，FreeFileSync 还提供了自定义功能，可以用户根据自己的需要更加灵活地自定义操作，赞~

Compare Advance

其实 Compare Advance 官方对它的定义更加倾向于文件夹对比工具而不是文件夹同步，利用Compare Advance可以非常方便地找出两个文件夹中哪些文件是哪些文件是A（或者B）文件夹特有的，哪些是共有的，哪些是不同的，生成的信息图以及数据非常详细。对于一些需要做大量文件分析的工作的人来说，这个可是利器呀~

当然，既然分析得都如此彻底了，那么进行同步操作也无非就是一个命令的事情， Compare Advance 的同步功能也很强大，按 Ctrl + Y 就可以在分析之后调出同步面板，在这里也可以设置同步的模式，也很方便。

写在后面：

虽然现在使用各种云端网盘备份文件已经很方便了，但是在一些不能上网的场合，或是一些敏感的不放心摆到互联网上去的文件（这些文件中很多又是重要的），还是在本地多建立备份会比较好，而那样的话，上面介绍的这几个软件就很适合你了~好了，说了这么多相信你心中也有了比较中意的那款软件了吧：） Enjoy吧！