Backing up open and locked file

Starting from version 2.6, Syncrify can backup opened and locked files. This feature only applies when running on Microsoft Windows platform.

Volume Shadow Copy (VSS)

Many applications running on Microsoft Windows OS can choose to lock their data files. This often create problems when other applications, such as Syncrify client, want to read these files during backup. Volume Shadow Copy or VSS, is a technology included in Microsoft Windows that allow taking manual or automatic backup copies or snapshots of data, even if it has a lock, on a specific volume at a specific point in time over regular intervals.

Enabling VSS in Syncrify

VSS is automatically enabled in Syncrify when you check the box for Backup locked files. See image below.

Prerequisites for using VSS

Following prerequisites must be met before using this options:

Operating system

You must be using Syncrify client on Windows XP, 2003, Vista, Windows 7 or 2008. VSS is not available on Windows 2000.

User privileges

Using VSS on Windows is considered a privileged task available to users belonging to the Administrator group. Therefore, ensure you are using a user account with enough privileges.

No additional steps are required if client is running on Windows XP or Windows 2003.

Extra steps are required, however, if you are running Syncrify on Windows 7, Vista or 2008. These steps satisfy the restrictions imposed by UAC., which limits software to run under standard privileges until an administrator authorizes an elevation.

Backup jobs are typically run in the background without any human interaction and therefore, it is not practical for someone to click Yes to the UAC prompt displayed by the OS.

You have one of two options when dealing with UAC:

Disable UAC. Click here for more information.

OR
Run the backup task as NT AUTHORITY\SYSTEM, instead of the regular user. If a backup task is run using NT AUTHORITY\SYSTEM, UAC will not prompt the user for additional privileges. Click here to see how to change the user ID.

Required services

VSS requires following services to be running on Windows.

COM+ System Application
Distributed Transaction Coordinator

Syncrify client will attempt to start these services if they are not running, provided the user ID has enough privileges.

OS Architecture

You cannot use 32bit version of Syncrify client if running on 64-bit version of the OS. You must download the 64-bit version of Syncrify client in order to use VSS. VSS does not work with Windows WOW (Windows on Windows).

Using Two-way sync with VSS

VSS creates a read-only copy of the locked files. Therefore, Syncrify won't be able to fetch a newer copy from the server if the file on the client is locked. In such cases, you will see an error in the log file and Syncrify will skip the file.

Disadvantage of using VSS

The time to backup increases significantly when you use VSS. This speed difference is more prominent if you have large files. Syncrify needs to calculate the MD5 signature of every file during backup. To speed up the matching process, these signatures are cached for files larger than 10 MB. This cache is not used when using VSS, which can significantly slow down the matching process.

Therefore, we recommend you use this feature only if you are sure you have open and locked files. Moreover, consider separating profiles for files that are locked and the ones that may be opened but not locked.

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