Data Rewind Overview

Data Rewind allows administrators to change the contents of a replicated volume to any point in time using rewind and advance operations. This capability is made possible through the Rewind Log which records all data changes that occur on the volume. As long as a timestamp is contained in the Rewind Log, the volume can be rewound to that point in time and can then be rewound further back in time or advanced forward in time.

The Rewind Log is created and maintained on a mirror Target system. All rewind and advance operations are performed on the Target to ensure minimal impact on the Source (primary) server. By default, rewind is disabled on all replicated volume resources. From the Volume Resource Properties page, select the Rewind Settings button to enable rewind for the selected replicated volume resource.

For optimal performance, the rewind log file should be on a separate physical disk. It is also recommended that write caching be enabled for the physical disk where the log is located and for the physical disk where the replicated data is located. To enable write caching, go to My Computer ->right-click Volume -> Properties -> Hardware tab -> Properties ->Policies tab -> Enable write caching on the disk.

If the Rewind Log file is to be stored at a different location than the default, this change must be made prior to enabling rewind for the selected replicated volume resource. From the Volume Resource Properties page, select the Rewind Settings button to change the location of the rewind log for the selected replicated volume resource.

To save space on your rewind log disk, you can choose to enable NTFS compression for the rewind log file. NTFS compression must be enabled prior to enabling rewind for the selected replicated volume resource. From the Volume Resource Properties page, select the Rewind Settings button to enable NTFS compression for the rewind log file.

After performing rewind/advance operations and locating good data, there is one recovery option available:

• Manually copy data to the Source (primary) server from the Target (backup) server. After manual copy is complete, a partial resync to the Target will be performed.

*Note: If Rewind is enabled and the DataKeeper Service is not running, a RewindDump file is created. Once the DataKeeper service starts, this RewindDump file is processed and removed, and the actual Rewind Log file is created. If you no longer want Rewind enabled on a particular volume, disable Rewind on that volume and then manually remove the RewindDump file.