Understanding the Plex State Cycle

Changing plex states are part of normal operations, and do not necessarily indicate abnormalities that must be corrected. A clear understanding of the various plex states and their interrelationship is necessary if you want to be able to perform the recovery procedures described in this chapter.

The figure, Main Plex State Cycle, shows the main transitions that take place between plex states in VxVM. (For more information about plex states, see the chapter "Creating and Administering Plexes" in the VERITAS Volume Manager Administrator's Guide.)

Main Plex State Cycle

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At system startup, volumes are started automatically and the vxvol start task makes all CLEAN plexes ACTIVE. At shutdown, the vxvol stop task marks all ACTIVE plexes CLEAN. If all plexes are initially CLEAN at startup, this indicates that a controlled shutdown occurred and optimizes the time taken to start up the volumes.

The figure, Additional Plex State Transitions, shows additional transitions that are possible between plex states as a result of hardware problems, abnormal system shutdown, and intervention by the system administrator.

When first created, a plex has state EMPTY until the volume to which it is attached is initialized. Its state is then set to CLEAN. Its plex kernel state remains set to DISABLED and is not set to ENABLED until the volume is started.

Additional Plex State Transitions

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After a system crash and reboot, all plexes of a volume are ACTIVE but marked with plex kernel state DISABLED until their data is recovered by the vxvol resync task.

A plex may be taken offline with the vxmend off command, made available again using vxmend on, and its data resynchronized with the other plexes when it is reattached using vxplex att. A failed resynchronization or uncorrectable I/O failure places the plex in the IOFAIL state.

Recovering an Unstartable Mirrored Volume, and subsequent sections describe the actions that you can take if a system crash or I/O error leaves no plexes of a mirrored volume in a CLEAN or ACTIVE state.

For information on the recovery of RAID-5 volumes, see Failures on RAID-5 Volumes and subsequent sections.