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quorum disk

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newunix
Frequent Advisor

quorum disk

can u please explain me why quorum disk was used
13 REPLIES
Duncan Edmonstone
Honored Contributor

Re: quorum disk

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

HTH

Duncan
Muhammad Ahmad
Frequent Advisor

Re: quorum disk

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
Frequent Advisor

Re: quorum disk

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
Super Advisor

Re: quorum disk

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
Frequent Advisor

Re: quorum disk

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. #
Honored Contributor
Solution

Re: quorum disk

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
Don't fix what ain't broke
R.K. #
Honored Contributor

Re: quorum disk

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).
Don't fix what ain't broke
newunix
Frequent Advisor

Re: quorum disk

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
Frequent Advisor

Re: quorum disk

Hi Ajeesh

can i have the steps for mirroring and editing the auto file
R.K. #
Honored Contributor

Re: quorum disk

Yes, you are correct.

>> how will set the quorum to a vg..
>> using vgchange -q y vgname
No need for that. Enforce the quorum requirement is the default. Since it ensures the integrity of the LVM configuration information, it is normally not advisable to override the quorum.

We only use "-q n" if we want to override quorum requirement for some troubleshooting.

>> steps for mirroring
Steps are different in PA-RISC and ITANIUM.
Refer guide for both procedures:
http://docs.hp.com/en/5991-1236/When_Good_Disks_Go_Bad_WP.pdf


>> editing the auto file
For Itanium systems:
# mkboot -a "boot vmunix -lq" /dev/rdsk/cXtYdZ
OR
# echo "boot vmunix" > ./AUTO
# efi_cp -d /dev/rdsk/c2t0d0s1 ./AUTO /efi/hpux/auto


Hope this helps.
Don't fix what ain't broke
Prasanth Thomas
Valued Contributor

Re: quorum disk

AVV
Super Advisor

Re: quorum disk

Hi,

You can get the steps from the below link both for IA and PA servers.

http://docs.hp.com/en/5991-1236/When_Good_Disks_Go_Bad_WP.pdf
newunix
Frequent Advisor

Re: quorum disk

thanks for all ur responses