Quorums

Find information about quorums.

A quorum exists when a majority of Volume Group Descriptor Areas and Volume Group Status Areas (VGDA/VGSA) and their disks are active. A quorum ensures data integrity of the VGDA/VGSA in the event of a disk failure. Each physical disk in a volume group has at least one VGDA/VGSA. When a volume group is created onto a single disk, the volume group initially has two VGDA/VGSA on the disk. If a volume group consists of two disks, one disk still has two VGDA/VGSA, but the other disk has one VGDA/VGSA. When the volume group is made up of three or more disks, each disk is allocated just one VGDA/VGSA.

A quorum is lost when enough disks and their VGDA/VGSA are unreachable so that a 51% majority of VGDA/VGSA no longer exists.

When a quorum is lost, the volume group deactivates itself so that the disks are no longer accessible by the logical volume manager. This prevents further disk I/O to that volume group so that data is not lost or assumed to be written when physical problems occur. As a result of the deactivation, the user is notified in the error log that a hardware error has occurred and service must be performed.

A volume group that has been deactivated because its quorum has been lost can be reactivated by using the activatevg -f command.