What is quorum disk in LVM?

[Ajin_1]

Dear Sir
What is quorum disk in LVM?..What is its use?What are the files found in this disk??
Please reply
Ajin.S

[Michael Steele_2]

a) There is no quorum disk in LVM
b) There is a quorum disk in MC/SG

In MC/SG a quorum disk is one disk shared by both nodes in a cluster. It is neither local to nodea or nodeb. It physically resides in between both nodes, is cabled together by both nodes and is seen in LVM by both nodes.

In MC/SG all LVM work is performed just like in a stand alone machine except there is a MC/SG configuration file that's used to activate the VG's and mount the file systems. In this configuration file you will also find a lock disk and a lock VG.

Its purpose is to determine the node winner in the race between the nodes at boot up or cluster reformation. First node to grab the lock disk wins the right to form the cluster.

[P Arumugavel]

Hi,

In addition to above, there is a concept called quorum in LVM.

Normally, volume groups are automatically activated during system startup. Unless you intentionally deactivate a volume group using vgchange, you will probably not need to reactivate a volume group.

However, LVM does require that a "quorum" of disks in a volume group be available. During normal system operation, LVM needs a quorum of more than half of the disks in a volume group for activation. If, during run time, a disk fails and causes quorum to be lost, LVM alerts you with a message to the console, but keeps the volume group active.

When booting the system, LVM also will require a quorum of one more than half of the disks in the root volume group. This means, for example, that LVM cannot activate a two-disk root volume group with one of the disks offline. As a result, if this happens, you will have a problem booting.

Rgds...

[Ismail Azad]

Hey Ajin,

If you are talking strictly based on LVM and not Serviceguard, there is a concept of quorum but the concept being a restriction that is imposed by LVM which is called as activation quorum and also running quorum.

Standard LVM imposes this restriction on a volume group be it vg00 or let's say vgora. The restriction always holds unless specified by the administrator to boot in low quorum or to override the restriction with vgchange. Activation quorum is associated with 51% of the available disks and running quorum with 50% of the available disks. Do understand that this restriction has absolutely nothing to do with space but has everthing to do with the availability of a disk. When the /sbin/lvmrc script executes unless specified otherwise for the activation of a volume group the quorum will be checked. Don't forget to assign points.

Regards
Ismail Azad