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About Quorum disk

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Lionel Liu
Advisor

About Quorum disk

Hello there,

We have two nodes cluster system with a Quorum disk.

When quorum disk fail, Can those two nodes still startup?

How to restore the Quorum disk if we don't have data backup for Quorum disk?

if we want to change quorum disk from dkc103 to dkc104. what the procedure would be?

Thanks very much

Lionel

7 REPLIES
Uwe Zessin
Honored Contributor
Solution

Re: About Quorum disk

With two nodes and a quorum disk, it depends on the parameter setting (VOTES, QDSKVOTES and EXPECTED_VOTES) whether both nodes can come up properly - normally, the answer is YES. It is still possible to do a conversational boot and alter the system parameters.

You don't need any special actions for 'restoring' the quorum disk. Just make sure the system sees a properly initialized disk and QUORUM.DAT will be created automatically. As this requires a running system, one might have to temporarily alter parameters like EXPECTED_VOTES to get the system fully running.

Changing the quorum disk should be done in one 'bang':

- make sure DKC104: is properly set up (initialized).

- update MODPARAMS.DAT on both nodes (DISK_QUORUM=) and run AUTOGEN to the SETPARAMS phase.

- shutdown both nodes

- boot both nodes again

- watch the boot sequence - one system should tell you that it has created QUORUM.DAT

- login and remove the old QUORUM.DAT from DKC103:[000000]
.
Mobeen_1
Esteemed Contributor

Re: About Quorum disk

Lionel,
It depends on how your system has been configured depending on the parameter settings for VOTES, QDSKVOTES and EXPECTED_VOTES

As Uwe mentioned at any point if you system is configured not to boot up in the scenario mentioned by you. You could always boot up MIN (conversational) and change the params and continue

With two nodes and a quorum disk, it depends on the parameter setting (VOTES, QDSKVOTES and EXPECTED_VOTES) whether both nodes can come up properly - normally, the answer is YES. It is still possible to do a conversational boot and alter the system parameters.

VOTES - How many votes the node contributes
to the VMS Cluster

EXPECTED_VOTES - Total no. of votes expected
the the full VMS Cluster is
bootstrapped

The following document should give you adequate information
http://h71000.www7.hp.com/doc/82FINAL/6318/aa-q28lh-tk.PDF

As for your second question, how to restore the quorum disk, i would follow exactly Uwe's suggestion.

You don't need to backup a quorum disk, if you would need to change the quorum disk, just specify it and initialise your old quorum disk and when the node boots up, it will create a quorum.dat on the disk you specified automatically

regards
Mobeen
Uwe Zessin
Honored Contributor

Re: About Quorum disk

Mobeen,
a conversational boot is not the same as a MINimum boot.

The first one is a mechanism to tell the operating system to stop in the early boot phase at the
SYSBOOT>
prompt so that you can view and change parameters. This is done at the console level, e.g.:
>>> boot -flags 0,1

One of these parameters is "STARTUP_P1". By setting it to "MIN" you tell the operating system to do a 'minimum boot'. One result is that the site specific startup procedure (SYSTARTUP_VMS.COM) is not run.
.
Jan van den Ende
Honored Contributor

Re: About Quorum disk

Lionel,

I am mostly with Uwe and Mobeen, except Mobeen's:


.. and initialise your old quorum disk ..


This is a heavy overkill!

If there is _ANY_ data on that disk other then QUORUM.DAT, you would loose it also!

So, _DO NOT_ initialise, but follow Uwe's suggestion, and just DELETE QUORUM.DAT.

Of course, double-check that you do delete it on the OLD, and NOT on the NEW Quorum disk! (this kind of mistake has been known to happen!) :-(

hth.

Proost.

Have one on me.

Jan
Don't rust yours pelled jacker to fine doll missed aches.
Mobeen_1
Esteemed Contributor

Re: About Quorum disk

Uwe,
Thanks for your suggestion... agree with you on the site specific startup procedure :)


.. and initialise your old quorum disk ..


Jan >This is a heavy overkill!

Mobeen> Purely matter of personal preferences as it will certainly not cause any harm doing this....agree with you that its little bit of extra work...but then think of it...for any future use, you would have to init the disk...so the question is why not now :)


If there is _ANY_ data on that disk other then QUORUM.DAT, you would loose it also!

No right or wrong...but i wouldn't suggest any body to have any other data on the quorum disk...
Well this could be debated at length .. depending on many factors :)

regards
Mobeen
Jan van den Ende
Honored Contributor

Re: About Quorum disk

Mobeen,

I agree with your ideas but..


No right or wrong...but i wouldn't suggest any body to have any other data on the quorum disk...


... is fully true for Tru64, but for VMS?

Maybe at today's disk prices you are getting righter & righter, but in the time when I last maintained clusters WITH Quorum Disk (before the SCSI era) a disk was a BIG investment, and there is no valid reason NOT to use it for data, as long as you (I mean: your management) do not need that specific data to be shadowed.

_I_ never saw any Quorum Disk that was not also used to store data...

fwiw,

Proost.

Have one on me.

Jan
Don't rust yours pelled jacker to fine doll missed aches.
Mobeen_1
Esteemed Contributor

Re: About Quorum disk

Jan,
Agree with you ..
Understand that disks were costlier than the present RAMs earlier days :)

regards
Mobeen