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Quorum Disk Compatilbility

 
Heinz W Genhart
Honored Contributor

Quorum Disk Compatilbility

Hi all
During the Itanium Migration I did the last few weeks, with 4 test-clusters and two production clusters, I encountered a problem with the quorum Disk.

My customer is migration a large application from Alpha to Itanium on one side, and a part of the application from OpenVMS to Linux on the other side. During this migration phase, we need a development cluster with 1 Alpha OpenVMS 7.3-2, 2 Alphas with OpenVMS 8.3 and 3 itanium Systems with OpenVMS 8.3-1H1. This is the facts.

I built this cluster with cloned systemdisks from other, very well running systems, where I build the systemdisks earlier. On the new development cluster I restored first the IA64 Systemdisk and then I brought up the 3 Itanium Systems. During this time the QUORUM.DAT file has been created. Then I restored the OpenVMS 8.3 Systemdisk for Alpha. No problem to boot and configure also this two systems.

Last, I restored the OpenVMS 7.3-2 Systemdisk, but then I was unable to boot. The system became Cluster Member, but was hanging then forever. See Attachement.

I did a lot of testing and finally I found the following solution:

I had to shutdown the whole cluster. I booted the DVD of IA64 System. Then I initialized the Quorumdisk with /NOGPT and finally I booted the OpenVMS System (with adjusted Votes) as first member into the cluster, mounted the quorumdisk and let create the 7.3-2 system the QUORUM.DAT file. After this I could boot the other 5 Systems too and have now the development cluster we need. My problem is solved so far, but there are questions.

- Is a quorum file created by an IA64 with OpenVMS 8.3-1H1 not compatible, that also a OpenVMS 7.3-2 System can use it?

- Is it the GPT.SYS on the quorumdisk which makes the problem

The second question is, because I did not initialize the quorumdisk first. I deleted only quorum.dat first, but then the 7.3-2 system did not boot as well. The 7.3-2 system booted first time after initializing the quorumdisk with /NOGPT.

Regards

Geni
7 REPLIES 7
John Gillings
Honored Contributor

Re: Quorum Disk Compatilbility

Geni,

When you cloned your system disks, did the new systems get new SCSSYSTEMIDs and SCSNODE values? Presumably you're talking about a cloned quorum disk too?

I'm not sure how much stuff goes into QUORUM.DAT, but it obviously must be tied to the cluster somehow. Given that, and the ease of creating a new quorum disk, I'd recommend creating a new from scratch for any new cluster. Reusing a cloned quorum disk doesn't really buy you anything (other than problems, given this posting!).

That's if I was going to use a quorum disk at all - something to be avoided, if at all possible. Lots of limitations and problems, without much payoff once you get to 3 nodes. You're talking about a 6 node cluster, why do you need a quorum disk at all?

If you want a definitive answer, you'll probably need to raise a formal case with HP Customer Support. My guess is the answer will be "not supported, use the documented mechanisms for creating a quorum disk".
A crucible of informative mistakes
Heinz W Genhart
Honored Contributor

Re: Quorum Disk Compatilbility

Hi John

I cloned the systemdisks, but I did not clone the quorumdisk.

That is exactly the finding I have. I used a Itanium System with OpenVMS 8.3-1H1 to initialize the quorumdisk and to create quorum.dat first. The 7.3-2 System then became cluster member but hangs at the point decribet in the attachement of my first post.

After deleting the quorumfile, I tried to recreate it with the 7.3-2 system, but without success.
Only now, after initializing the quorumdisk again with /nogpt the 7.3-2 system was able to boot and to create the quorumfile.

So I have to asume, that a 8.3-1H1 quorumdisk initialized with /gpt is not backward compatible with OpenVMS 7.3-2

The reason why we are using a quorumdisk is:

- we want be able to boot a single machine into the cluster (development cluster)

- The another clusters, have two Alpha and two itanium systems only during the migration phase. After migration, we will remove the two alphas and then we need a quorumdisk.

regards

Geni
Wim Van den Wyngaert
Honored Contributor

Re: Quorum Disk Compatilbility

No idea if this is related but did you install the required patches ?
http://h71000.www7.hp.com/doc/83final/6677/6677pro_sm2.html

Wim
Wim
Volker Halle
Honored Contributor

Re: Quorum Disk Compatilbility

Geni,

the ODS-2 change regarding GPT.SYS is described in the V8.2 Release Notes:

http://h71000.www7.hp.com/doc/82final/6674/6674pro_sm.html#odschanges

Maybe the quorum disk code on V7.3-2 makes the 'wrong assumptions' about the disk layout when trying to find the QUORUM.DAT file on the quorum disk ?

Volker.
Volker Halle
Honored Contributor

Re: Quorum Disk Compatilbility

Geni,

the following message is missing. It would have been issued by [SYSINI]SYSINIT, after it would have successfully opened the quorum file (using the primitive file system):

%SYSINIT-I- found a valid OpenVMS Cluster quorum disk

A node should be able to join the cluster, even if it cannot (directly) access the quorum disk. It may not be able to form the cluster, if it's being booted as the first node and it depended on QDSKVOTES to be able to reach quorum.

Volker.
Michael Moroney
Frequent Advisor

Re: Quorum Disk Compatilbility

The quorum disk code is very primitive and does not go through standard RMS, since it has to work before the node joins a cluster, and it can't be blocked when there is no quorum, of course. There is special code that locates the quorum file that runs before the node joins a cluster.

I'll bet that the code that locates the quorum file has never been taught about GPT, and initializing the disk /NOGPT should take care of things. After the disk is initialized, the cluster must be "up" at some point without needing the quorum disk's votes in order to create the quorum disk the first time (since I'm pretty sure that goes through RMS) but that's the a one time deal.
Heinz W Genhart
Honored Contributor

Re: Quorum Disk Compatilbility

Hi all

I close this thread, because we encounterd another very funny problem on this cluster. For this thread and for the new problem I will open another thread called 'Problems with different version of the operating system in same cluster'

Best regards

Geni