Using quorum
Quorum ensures that more than half of the physical disks in a volume group are available.
Quorum does not keep track of logical volume mirrors, and is therefore not a useful way to ensure data availability. You can lose quorum when you still have all your data. Conversely, you can lose access to some of your data, and not lose quorum.
Quorum is beneficial for volume groups on RAID arrays, such as the ESS and IBM® TotalStorage® DS Series. The RAID device provides data availability and recovery from loss of a single disk. Mirroring is typically not used for volume groups contained entirely within a single RAID device. If a volume group is mirrored between RAID devices, forced varyon can bring a volume group online despite loss of one of the RAID devices.
Decide whether to enable or disable quorum for each volume group. The following table shows how quorum affects when volume groups varyon and off:
| Condition for volume group to varyon | Condition for volume group to vary off | |
|---|---|---|
| Quorum enabled | More than 50% of the disks in the volume group are available | Access is lost to 50% or more of the disks |
| Quorum disabled | All of the disks in the volume group are available | Access is lost to all of the disks |
Quorum checking is enabled by default. You can disable quorum by using the chvg -Qn vgname command, or by using the smit chvg fastpath.