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标题
Slow transfer speeds on agent protected SQL servers with heavy write operations -
说明
On some SQL servers we have observed slow transfer speeds (backups) when taking incremental backups of volumes that have heavy write activity especially when that write activity is affecting the same blocks of data on the volume. Generally a base image backup will run at "normal" speeds (20+ MB/s) while an incremental will run significantly slower (100-500 KB/s). -
原因
When the same blocks of data on a volume are being changed rapidly (as much as multiple times per minute) the Rapid Recovery agent is unable to effectively gather the blocks of data to be backed up and transfer them to the core. -
解决办法
To work around this issue, we have created a registry value that can be changed which manipulates the way the Rapid Recovery agent reads data from a volume during backup. This change has been seen to speed up incremental backups so that they run at close to the same speed as a base image backup. To implement this workaround:
- Open regedit
- Browse to HKEY_LOCAL_MACHINE\Software\AppRecovery\Core\Agents\\Transfer\CombineRequests where is the unique ID of the agent where you are experiencing slow backup speeds.
- Set CombineRequests = 1 (this turns the setting on)
- The setting will only take effect for the next backup
We do not recommend enabling this setting for all agents, just for ones experiencing this exact issue.
Windows Registry Disclaimer:
Quest does not provide support for problems that arise from improper modification of the registry. The Windows registry contains information critical to your computer and applications. Make sure you back up the registry before modifying it. For more information on the Windows Registry Editor and how to back up and restore it, refer to Microsoft Article ID 256986 “Description of the Microsoft Windows registry” at Microsoft Support.