Persistent FastResync of volume snapshots

If persistent FastResync is enabled on a volume, VxVM uses a FastResync map to keep track of which blocks are updated in the volume and in the snapshot.

When snapshot volumes are reattached to their original volumes, persistent FastResync allows the snapshot data to be quickly refreshed and re-used. Persistent FastResync uses disk storage to ensure that FastResync maps survive both system and cluster crashes. If persistent FastResync is enabled on a volume in a private disk group, incremental resynchronization can take place even if the host is rebooted.

Persistent FastResync can track the association between volumes and their snapshot volumes after they are moved into different disk groups. After the disk groups are rejoined, persistent FastResync allows the snapshot plexes to be quickly resynchronized.