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FastResync enhancements

FastResync provides the following enhancements to VxVM:

Faster mirror resynchronization 

FastResync optimizes mirror resynchronization by keeping track of updates to stored data that have been missed by a mirror. (A mirror may be unavailable because it has been detached from its volume, either automatically by VxVM as the result of an error, or directly by an administrator using a utility such as vxplex or vxassist. A returning mirror is a mirror that was previously detached and is in the process of being re-attached to its original volume as the result of the vxrecover or vxplex att operation.) When a mirror returns to service, only the updates that it has missed need to be re-applied to resynchronize it. This requires much less effort than the traditional method of copying all the stored data to the returning mirror. 

Once FastResync has been enabled on a volume, it does not alter how you administer mirrors. The only visible effect is that repair operations conclude more quickly. 

Re-use of snapshots 

FastResync allows you to refresh and re-use snapshots rather than discard them. You can quickly re-associate (snap back) snapshot plexes with their original volumes. This reduces the system overhead required to perform cyclical operations such as backups that rely on the snapshot functionality of VxVM.