Veeam Changed Block Tracking Driver - Veeam Agent for Microsoft Windows Guide
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Veeam Agent for Microsoft Windows 2.2
User Guide

Veeam Changed Block Tracking Driver

You can set up Veeam Agent for Microsoft Windows to use the Veeam CBT driver instead of the default CBT mechanism. The Veeam CBT driver is a class filter driver for volume devices that helps Veeam Agent for Microsoft Windows keep track of changed data blocks in a more efficient way. The driver is intended for servers running applications with large database files.

To use the Veeam CBT driver, the Veeam Agent computer must meet the following requirements:

  • Run a Microsoft Windows Server OS
  • Run the Server edition of Veeam Agent for Microsoft Windows

Veeam Changed Block Tracking Driver Important!

Consider the following:

  • Prior to installing the Veeam CBT driver on a computer running Microsoft Windows Server 2008 R2, make sure that update KB3033929 is installed in the OS. To learn more, see https://www.microsoft.com/en-us/download/details.aspx?id=46083.
  • Do not install the Veeam CBT driver on a computer running Microsoft Windows Server 2008 R2, 2012 or 2012 R2 if one or more volumes on this computer are encrypted with Microsoft BitLocker (or other encryption tool), or if you plan to use Microsoft BitLocker to encrypt volumes on this computer. Concurrent operation of Microsoft BitLocker and Veeam CBT driver may result in driver failures and may prevent the OS from starting.

To enable the advanced CBT mechanism provided by the Veeam CBT driver, you need to install the driver in the Veeam Agent for Microsoft Windows control panel. You can perform this operation at any time you need. To activate the driver after installation, Veeam Agent for Microsoft Windows needs to reboot the computer. After computer reboot, the Veeam CBT driver will start keeping track of changed data blocks on computer volumes whose data you have selected for backup in the Veeam Agent backup job settings.

In contrast to the default CBT mechanism that supports NTFS volumes only, the Veeam CBT driver can keep track of changed data blocks on volumes that use the following file systems:

  • NTFS
  • FAT
  • ReFS

Information about changed data blocks is registered in special VCT files. VCT files are stored in the C:\ProgramData\Veeam\EndpointData\CtStore folder on the Veeam Agent computer. When the backup job runs, Veeam Agent for Microsoft Windows uses VCT files to find out what data blocks have changed since the last run of the job, and copies only changed data blocks from the backed-up volume.

Veeam Changed Block Tracking Driver Note:

Consider the following:

  • If the Veeam Agent computer shuts down unexpectedly, the Veeam CBT driver may fail to register information about changed data blocks in a VCT file. In this case, during the next backup job session, Veeam Agent for Microsoft Windows will need to read all data from the backed-up volume to create incremental backup. As a result, incremental backup will require greater time.
  • If data blocks are changed on a volume while this volume is mounted on another Windows-based machine, during the next backup job session, Veeam Agent for Microsoft Windows will also read all data from the volume to create incremental backup.
  • The Veeam CBT driver cannot detect data block changes made on a volume that is mounted in a non-Windows OS. For example, such changes can be made when you boot your computer using a Linux-based antivirus rescue disc. To continue the backup chain after such changes, you need to create active full backup instead of incremental backup. Alternatively, you can reset CBT. To learn more, see Resetting CBT.

Veeam Changed Block Tracking Driver

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