topic Re: set vol/size=xxxx in vms in Operating System - OpenVMS

set vol/size=xxxx in vms

edward wang_1 — Tue, 03 Mar 2009 08:59:07 GMT

my customer want to know whether have risk in application online to expand a cluster share disk size in a cluster system.
es45 cluster vms7.3-2+EVA 5000 storage, I know can do it,but no experience in a application online cluster.

Re: set vol/size=xxxx in vms

Robert Gezelter — Tue, 03 Mar 2009 09:24:04 GMT

Edward,

Done correctly, there is no risk that I am aware of.

Obviously, the storage containers must be larger than the declared disk size already. The SET VOLUME command only affects the OpenVMS file structure, not the underlying storage container on the EVA.

I discussed the process of increasing the size of dynamic volume during normal operation without interruption at several past HP Technology Forums. The most recent presentation was at the 2007 Forum in a session entitled "Migrating OpenVMS Storage Environments without Interruption or Disruption". The slides from that session are available at: http://www.rlgsc.com/hptechnologyforum/2007/1512.html

I always recommend care when doing any volume maintenance of this type. It is far easier to take precautions than it is to recover from a mistake. Also, since these changes can be done without disruption, I recommend that they be done gradually, not all in one step.

Lastly, I would not recommend experimenting on a production cluster. If this cluster is important, create a set of practice volumes and test the steps of the transition.

- Bob Gezelter, http://www.rlgsc.com

Re: set vol/size=xxxx in vms

Jan van den Ende — Tue, 03 Mar 2009 09:49:57 GMT

Edward,

wise words already written by Bob.

All I can add is personal experience: it went so easily, so fast, so well!
At the migration to EVA storage, we took the opportunity to INIT the volumes to maximize potential size, and whenever the need arose, incresed the SAN storage, and executed SET VOLUME. After the first few times it was just routine.

hth

Proost.

Have one on me.

jpe

Re: set vol/size=xxxx in vms

Hoff — Tue, 03 Mar 2009 13:07:00 GMT

So your customer is depending on you for information that you don't currently possess, and you don't know how to get that information. One wise move here is to bow out of the discussion and kick this over to somebody in your organization that does know how to do this.

Both Bob and Jan omit mention of some considerations that can arise with DVE, though both do correctly point to the potential risks of testing in production.

Here's a write-up with a few of the land-mines that are known, and do ensure the box is current on its ECO kits:

http://64.223.189.234/node/207

Re: set vol/size=xxxx in vms

John Gillings — Tue, 03 Mar 2009 20:40:11 GMT

edward,

"risk" depends on definitions, and the application itself.

The DVE mechanism is solid, and fairly well tested (though more so on a later versions of OpenVMS than you're running). We've expanded online volumes, on the fly, numerous times, without any problems (but I'm not sure we've done it on the most critical production systems).

However, if you want to guess at potential problems, look at the application. It's entirely possible there is an explicit or implicit assumption that disk size is static. For example, perhaps the application samples the volume size at startup? Perhaps a change in disk size could affect internal logic?

Try it on your test system first.

Re: set vol/size=xxxx in vms

Andy Bustamante — Tue, 03 Mar 2009 20:48:34 GMT

In addition to the comments above, make sure you're up to date on ECOs. If you're running a stock 7.3-2 system, there are are patches readily available from HP that should be applied.

Andy Bustamante

Re: set vol/size=xxxx in vms

edward wang_1 — Wed, 04 Mar 2009 00:42:07 GMT

Hi all of up
thank you so much for help.

Re: set vol/size=xxxx in vms

Robert Davidson_1 — Wed, 04 Mar 2009 20:16:59 GMT

A word to the wise. In the past my system had 3 HSG80 controllers each one having one member of a shadow set. When I went to issue the Set vol/size command during the middle of the day, on a very active unit both systems froze (free space was very low). We ended up crashing both the ES-40 and ES-45 and upon booting the system found that the unit had expanded to the new size. We had waited over 30 minutes (took some time to drive over to the site). So far we have had no problems expanding volumes since we recently switched over to an EVA 4400. We increased the volume sizes prior to moving the data over and then with no users on the system issued the set vol/size command with no problems.
Bob Davidson