quorum disk

[newunix]

can u please explain me why quorum disk was used

[Duncan Edmonstone]

why a quorum disk was used where? you really should provide more context...

I'm assuming as you have posted in the HP-UX forum you aren't referring to a MSCS quorum disk, and are in fact referring to a cluster lock disk in Serviceguard...

read this section of the Serviceguard manual:

http://docs.hp.com/en/B3936-90144/ch03s02.html#babggaac

HTH

Duncan

[Muhammad Ahmad]

The cluster lock is implemented by means of a lock disk, lock LUN, or a Quorum Server.

The cluster lock is used as a tie-breaker only for situations in which a running cluster fails and, as Serviceguard attempts to form a new cluster, the cluster is split into two sub-clusters of equal size. Each sub-cluster will attempt to acquire the cluster lock. The sub-cluster which gets the cluster lock will form the new cluster, preventing the possibility of two sub-clusters running at the same time. If the two sub-clusters are of unequal size, the sub-cluster with greater than 50% of the nodes will form the new cluster, and the cluster lock is not used.

I hope the above helps in understanding the core concepts.

[newunix]

when i was reading the docs for lvm ,,

it was that

volume groups must have quorum

what does it related to??? and y it is used for ?

[AVV]

Hi,

We are normally using this on root volume ,vg00. We will mirror the root disk with another disk for redundancy. Did you ever notciced that ,we will edit AUTO file after doing the mirroring of the same as below

boot vmunix -lq

Why we use it ?

This is because, more than 50% of disk (quorrum)presents should be there to activate the VG incase of mirroring.In this case we may have only two disks and if one goes down...50% is only there. So, activating vg00 and booting becomes a problem here. To overcome that, we are using that AUTO file editing.

Hope you had a little light over there !!

[newunix]

Hi Ajeesh

wat i understand from ur reply is

we are having two disk one as primary and secondary disk

i have created a mirror disk

after then we have to boot in

boot vmunix -lq

edit the auto file

if i am wrong correct me

[R.K. # · Accepted solution]

Hello Newunix,

>> volume groups must have quorum
Apart from root VG, suppose a non-root Vg has 2 disks that are NOT mirrored and one disk goes bad and then you try to activate that VG, you will get same error (not in quorum).

So, even if disks are mirrored or not, more than 50% of the disks present should be working.
In such cases you can still activate the vg by:
# vgchange -a y -q n vgname

[R.K. #]

Hello Again,

>> boot vmunix -lq
Above command should be used for setting secondary bootable disk only. Since ideally server will try to boot from secondary disk only when primary fails. So if we have this setting (-lq), then quorum condition will be over-ruled and system will be booted without halting at ISL. But then you might not find that the primary has gone bad (unless you get alerts).

[newunix]

Hi RK

vgchange -a y -q n vgname

-q n option used to activate the vg when quorum is not maintained..

as per my understanding from ur post

1. if there are two disks in a vg and if one disk goes fails quorum will not be maintained.

even at the time we can use

vgchange -a y -q n vgname ( to activate that vg.. which has a failed disk.) if we acheived quorum before.


if i am wrong in the above plz guide me


and more

how will set the quorum to a vg..

using vgchange -q y vgname

[newunix]

Hi Ajeesh

can i have the steps for mirroring and editing the auto file