Veritas Volume Manager - Plexes

In Veritas Volume Management, disk spaces is allocated as sub-disks, plexes and eventually volumes. Contiguous disk blocks are grouped as sub-disks, which is a portion on the Vx Disk. 

Plex is a group of sub-disks. Plex can be organized as stripes, mirror and RAIDs. Plexes are used to form volumes.

'vxassist' command automatically creates plexes while creating volumes. Plex can also be created seperately with 'vxmake' command and attached to a volume later.

'vxprint' command is used to display plex information. (vxprint -g -l plex)

Plex States:

VxVM maintains the state of plex automatically. There are many state associated with plex which helps to identify the consistency of data. These states are very important for the recovery of volume after a system failure.

ACTIVE State: 
This state shows the plex is in use and I/O operation is happening on the plex.

CLEAN State:

If a plex has consistent data, this state is set.

EMPTY State:

This is set when a new volume is created and plex is not initialized. 

OFFLINE State:

Plex is not associated with a volume.

Plex Condition Flags:

NODEVICE:

The physical disk associated with sub-disk of plex is not available. Recovery has to be done to be able to use the plex again.

RECOVER:

The physical disk associated with plex is reattached but but is not in sync with volume and recovery is needed.

REMOVED:

The sub-disk associated with a plex is lost. Complete recover of the sub-disk is needed.

Plex Kernal State: This indicates if plex is accessible for volume driver. maintained internally, state change is reflected automatically.

DETACHED:

Plex is in maintenance state. No write access is allowed on plex.

DISABLED:

Plex is not accessible.

ENABLED:

Plex is online and read/write access is accepted.