Please refer to the following topics for ways to improve SIOS DataKeeper performance.

SIOS DataKeeper Intent LogSIOS DataKeeper uses an intent log (also referred to as a bitmap file) to track changes made to the source, or to the target volume when the target is unlocked. This log is a persistent record of write requests which have not yet been committed to both servers. The intent log gives SIOS DataKeeper the ability to survive a source or target system failure or reboot without requiring a full mirror resync after the recovery of the system. There is a performance overhead associated with the intent log, since each write to the volume must also be reflected in the intent log file. To minimize this impact, it is recommended that the intent logs be stored on a physical disk that is not involved in heavy read or write activity. See Relocation of Intent Log for more information.

Compression – DataKeeper allows the user to choose the compression level associated with each mirror. Enabling compression can result in improved replication performance, especially across slower networks. A compression level setting of 3-5 represents a good balance between CPU usage and network efficiency based on the system, network and workload. The compression level of a mirror can be changed after the mirror is created. See Changing the Compression Level of an Existing Mirror.

High-Speed Storage Best Practices – If the DataKeeper default bitmap location (%ExtMirrBase%\Bitmaps) is not located on high-speed storage, you should move the bitmaps to a high-speed storage device in order to eliminate I/O bottlenecks with bitmap access. To do this, allocate a small disk partition, located on a high-speed storage drive, on which to place the bitmap files. Create the folder in which the bitmaps will be placed, and then Relocate the bitmaps (intent logs) to this location.


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