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TruCluster Confusion

Kapil Jha
Honored Contributor

TruCluster Confusion

Hello Gurus
I have some very basic doubts please clear them.
lets say we have 2 node cluster 1 quorum disk

Condition 1:
if cluster was running and quorum disk went currupted what will happen to clster.
for me it shouls work.

Condition 2
Now second standby member goes down at this time what will happen to cluster.
for me it should work

Condition 3:
quorum is down and both member is down.h/w problwm in second member.So only one member can come up at this time.
I think cluster wont come up.

Pleae clear this!!!!
I am in this small bowl, I wane see the real world......
9 REPLIES
Venkatesh BL
Honored Contributor

Re: TruCluster Confusion

I don't think Condition 2 will work. Quorum disk is used to ensure that a cluster can be formed even when you have less than 50% of the nodes UP. So, in the case of 2 node cluster, a single node without a Quorum cannot boot as a cluster.

http://h30097.www3.hp.com/docs/base_doc/DOCUMENTATION/V51B_HTML/ARHGYETE/MNGCNXCH.HTM talks more about the quorum votes, usage etc.
Rob Leadbeater
Honored Contributor

Re: TruCluster Confusion

Hi,

The outcome will depend on how many votes are configured for the hosts and the quorum disk, however for a standard configuration, each host would have one vote, and the quorum disk would have one vote.

For a two node cluster with a quorum disk, the votes needed to have quorum would be two.

Therefore:

Condition 1: Votes would be two, so the cluster would still work.

Condition 2: Votes would be one, so the cluster would hang.

Condition 3: Cluster wouldn't boot. You would need to modify the quorum votes to one to get it to boot.

Hope this helps,

Regards,

Rob
Kapil Jha
Honored Contributor

Re: TruCluster Confusion

yeh
for condition 2
I thought cluster would keep on working as quorum vote is already with 1st member and if quorum is currupted nothing happen(I thought its just boot time process to allocate votes). 1st member have vote and would keep on serving cluster if second member goes down.
I am in this small bowl, I wane see the real world......
Rob Leadbeater
Honored Contributor

Re: TruCluster Confusion

> I thought its just boot time process to allocate votes.

No. Votes are dynamic as the system is running.

Cheers,

Rob
Venkatesh BL
Honored Contributor

Re: TruCluster Confusion

Quorum votes are calculated whenever there is a membership change. They are used to ensure that the cluster is in a 'sane' state and that you don't end up with a 'divided' cluster.
Kapil Jha
Honored Contributor

Re: TruCluster Confusion

Hello Venkatesh,
What exactly you mean by membership change??
does it mean whenever there is some relocation???
if it is like this then cluster should keep on running when other member or quorum goes down.
Please stop me if I am wrong.
I am in this small bowl, I wane see the real world......
Hein van den Heuvel
Honored Contributor

Re: TruCluster Confusion

Condition 2 and 3 are the same.
A properly configured cluster member should refuse to start if not active, and should stop immediately if active.

The reason for this is that it is impossible to tell for the surviving node whether it is having a problem itself or whether the rest of its world has a problem and it is the sole surviver. There is nothing to talk to, to help decide.

If member 1 does not see the quorum disk, nor member 2, then it must assume there is a probllem with itself. As far as it is concerned, it must assume that quorum disk and member 2 are happily active in a cluster together and member 1 should not touch anything (and disk) that cluster would be assuming ownership of.

Now if you as uber-cluster manager decide you know better, then you could conceivably alter the normal settings and create a fresh cluster, with the intent to add member 2 as a new node if and when it comes back. But that would all be temporary and manual.

fwiw,
Hein.
Venkatesh BL
Honored Contributor

Re: TruCluster Confusion

The link I provided gives specific examples of what happens when a member goes down in a two node cluster - with Quorum, without Quorum. That should give you clear idea of the concept.
Kapil Jha
Honored Contributor

Re: TruCluster Confusion

confusion clear!!!!
I am in this small bowl, I wane see the real world......