Re: Quorum disk

On Thu, 09 Sep 1999 14:48:31 +0200, Doktor <doktor_at_post.pl> wrote:

Sun Cluster makes also use of the quorum. They call it 'quorum device', because it can be a single disk or a multi-host attached disk controller.

Starting up the cluster, the first node, the master, will do a SCSI reserve of the quorum device. If the 'heart beat' connection between the nodes of a Sun cluster fails, a reconfiguration process starts and all the nodes try to get (to reserve) the quorum device. But only one node will get it. All the other nodes will leave the cluster because they can't communicate with the master, helding the quorum, and they can't get the quorum. So for them, something is really wrong.

By the way, one really nasty thing with this is, that if the quorum device fails and any cluster reconfiguration starts, the WHOLE cluster will go down, because none of the nodes can get the (failed) quorum ..

We had such a situation.

Cluster configuration was the following. Oracle OPS, node1 and disk_array1 powered by UPS_1, node2 and disk_array2 powered by UPS_2. Disks in disk_array2 used as mirrors for disks in disk_array1. Node1 - master, node2 - slave. Quorum device was a disk in disk_array2. An power fail on UPS_2 accured, resulting in a power failing off node2 and disk_array2. Smart cluster starts a reconfiguration to configure node2 off the cluster. Node1 failed to get the quorum - and leaved the cluster too.

As a result the OPS database crashed completely.

Outcome of this was to buy an extra SSA controller with an extra UPS_3. The only purpose of this SSA controller was to play the role of the QUORUM DEVICE.

>It seems, that you are working with AlphaServers :-) Quorum disk is a
>disk with special software for starting VMS cluster (in a special
>configurations of such a cluster). It can be hard disk or floppy (!),
>'cause this software doesn't required a lot of capacity.
>
>Old Luke wrote:
>>
>> What is a quorum disk?
>>
>> Thanks!!!!

Silvio Seifert
Foehrer Strasse 34
65199 Wiesbaden
Germany Received on Sat Sep 11 1999 - 12:47:15 CDT