VxVM may need to perform several operations to restore fully the contents of a RAID-5 volume and make it usable. Whenever a volume is started, any RAID-5 log plexes are zeroed before the volume is started. This prevents random data from being interpreted as a log entry and corrupting the volume contents. Also, some subdisks may need to be recovered, or the parity may need to be resynchronized (if RAID-5 logs have failed).
VxVM takes the following steps when a RAID-5 volume is started:
DETACHED volume kernel state and setting the volume state to
REPLAY, and enabling the RAID-5 log plexes.
DETACHED volume kernel state and setting the volume state to SYNC. Any log plexes are left in the
DISABLED plex kernel state.
The volume is not made available while the parity is resynchronized because any subdisk failures during this period makes the volume unusable. This can be overridden by using the
unsafe start option with the
vxvol command. If any stale subdisks exist, the RAID-5 volume is unusable.
ENABLED volume kernel state and the volume state is set to
ACTIVE. The volume is now started.