topic Re: quorum server needs!!! in Operating System - HP-UX

quorum server needs!!!

gany59 — Tue, 22 Feb 2011 11:13:09 GMT

I have gone through the forum related to service guard, they have mentioned like for 2 node configuration, there is no need of quorum server. I want to know what is quorum server, is that a package, can we install that package on any of the server which is configured on the cluster environment. If hear beat fails on the 4 node cluster, then the each node will contact the quorum server right ?

basically what is the need of quorum server.
Thanks in advance!!

Re: quorum server needs!!!

Hakki Aydin Ucar — Tue, 22 Feb 2011 11:23:58 GMT

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Re: quorum server needs!!!

Ismail Azad — Tue, 22 Feb 2011 11:25:44 GMT

Hi,

You can use 2 methodologies for "cluster reformation" at the time of communication loss in terms of heartbeat between 2 nodes of the cluster :-

1)Lock disk which is a disk part of a VG which the nodes will "race" or compete for when heartbeat messages are not being received within NODE_TIMEOUT.

2)Quorum server is outside your serviceguard environment and for a 5 node cluster and more you cannot use a local LVM lock disk , you will have to make use of Q/S and the nodes continuously poll this server. {atleast in SGA.11.17 and before}

Dont forget to assign points.

Regards
Ismail Azad

Re: quorum server needs!!!

Rita C Workman — Tue, 22 Feb 2011 12:04:19 GMT

A quorum server provides the same mechanism as the lock disk. It provides quorum, which is defined as " the number of members of a group or organization required to be present to transact business legally, usually a majority.

So both provide a majority, thus allowing the cluster to reform and come up.

A quorum server is a piece of software that can be loaded on a number of devices. The only requirement is that the device must NOT be in the cluster.

Here is a whitepaper on Quorum Servers & you can also go out and download other guides on it. It is very simple to setup.

http://bizsupport2.austin.hp.com/bc/docs/support/SupportManual/c02057261/c02057261.pdf

Regards,
Rita

Re: quorum server needs!!!

gany59 — Tue, 22 Feb 2011 12:29:12 GMT

Hi Ismail,

I am unable to understand what u mentioned in the below lines:

"1)Lock disk which is a disk part of a VG which the nodes will "race" or compete for when heartbeat messages are not being received within NODE_TIMEOUT."

Sorry i am not aware of what the lock disk is do. I know that the disk which is shared between the all the nodes are called cluster lock disk right ?

And too if the we got the alert like cluster disk fails, then the cluster would be halted automatically right ? hence one group of disk called Vg and that Vg is shared between the nodes. So atleast there must be a data loss right ?

Please dont feel this questions are silly. I am handling cluster environment first time. thats y i have raised many questions in this forumn..... :)

Thanks!

Re: quorum server needs!!!

Stephen Doud — Tue, 22 Feb 2011 15:55:14 GMT

Hello gany59,
An arbitration device (lock disk, lock lun or quorum server) is required for a 2-node cluster.

If you will be building a cluster but do not have the opportunity to take HP Education Center training on the topic, at a minimum, you should take some time to read the "Managing Serviceguard" manual located at http://www.hp.com/go/hpux-SG-docs.

Re: quorum server needs!!!

nijokj — Tue, 22 Feb 2011 16:49:19 GMT

There are two different way to avoid split brain syndrome when the heartbeat failed .
One is lock disk and another is quarom server.
Lock disk is dedicated disk which is used as a arbitrary device when the cluster contain four or less than four node as per HP recomendation.
Quarom server uses as arbitration device when cluster includes morethan four nodes as per HP recoments,It is a seperated server installed with quarom software other than cluster node connected in cluster network.

Re: quorum server needs!!!

gany59 — Fri, 25 Feb 2011 07:30:43 GMT

So nijoki,

CLuster lock disk is the disk what we shared for the cluster nodes, say for an example, 2 node cluster. Am i right ?

Re: quorum server needs!!!

nijokj — Sat, 26 Feb 2011 10:45:21 GMT

you are correct ,cluster lock disk is a shared disk which should be accessible from all the nodes in cluster.

please refer the below pdf which is the best guide about these arbitration mechanisam of serviceguard cluster I have ever seen.

http://bizsupport2.austin.hp.com/bc/docs/support/SupportManual/c02056095/c02056095.pdf