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Expanding a RAID-5 array

 
Keith L Walker
Occasional Contributor

Expanding a RAID-5 array

We have a VMS 8.3 system with a Smart Array 5302 RAID controller. We have eight 9Gb drives configured as a 54Gb RAID-5 array with one hot spare.

If we hot-swap each 9GB drive for an 18Gb drive and let the array rebuild between swaps, we will eventually have a 54Gb array running on the larger drives. with 50% unused space.

Is there any way on VMS to expand the array into the empty space, producing a 108Gb volume?

According to the User Guide for the 5300 series controllers, "Not all operating systems support online capacity extension." Windows apparently does, but what about VMS?

TIA.
10 REPLIES 10
marsh_1
Honored Contributor

Re: Expanding a RAID-5 array

hi,

you can use the set volume/limit commands check out the dcl dictionary part 2 pg 322 or do a help on set volume.

http://h71000.www7.hp.com/doc/83final/9996/ovms_83_dcl_ref2.pdf

and also the system managers manual - look for dynamic volume expansion.


HTH



Highlighted
Andy Bustamante
Honored Contributor

Re: Expanding a RAID-5 array

>>> If we hot-swap each 9GB drive for an 18Gb drive and let the array rebuild between swaps, we will eventually have a 54Gb array running on the larger drives. with 50% unused space.

You'll have a Smart Array with a 54 GB logical unit configured. You need to expand the Smart Array logical unit.

To have OpenVMS expand into the resized logical unit, see the OpenVMS FAQ at HoffmanLabs.
http://64.223.189.234/node/207

Depending on your use, number of files and directories vs number of headers and initialized number of files, this may be the time to backup to tape, reinitialize and restore to a new unit.

With the current price of disk, why not 36 or 72 gb disks?

Andy Bustamante
If you don't have time to do it right, when will you have time to do it over? Reach me at first_name + "." + last_name at sysmanager net
Keith L Walker
Occasional Contributor

Re: Expanding a RAID-5 array

Why not 36 or 72GB drives? Because we have a ton of surplus 18Gb drives on hand. The only reason for contemplating the expansion is that it will cost us nothing.
Robert Gezelter
Honored Contributor

Re: Expanding a RAID-5 array

Keith,

OpenVMS has supported Dynamic Volume Expansion since release 7.3-2.

SET VOLUME/LIMIT can expand properly initialized volumes in place. Used in combination with Host Based Volume Shadowing, OpenVMS can do impressively dynamic migrations of storage.

In 2005 and 2007, I presented "Migrating OpenVMS Storage Environments without Interruption or Disruption" at the HP Technology Forum. The slides form the 2007 presentation can be found at: http://www.rlgsc.com/hptechnologyforum/2007/1512.html

- Bob Gezelter, http://www.rlgsc.com
Keith L Walker
Occasional Contributor

Re: Expanding a RAID-5 array

Thanks, Bob (and also Andy and Mark). I had read your presentation in my research prior to posting my question. However, all references I found, including yours, discuss DVE in the context of Volume Shadowing.

Since we aren't using Volume Shadowing, my question is really: Can you do something similar with hardware-based RAID? It is looking like the answer is no.

Thanks.
Zeni B. Schleter
Regular Advisor

Re: Expanding a RAID-5 array

We have smart Array controller on OpenVMS hosts. It has been three years since we set them up but I vaguely remember reading in a manual on the management of the Smart Arrays that dynamic expansion of the disks were not possible for the OpenVMS operating system. The way I understood it was that the Smart array could not take the logical device and expand it to be larger. Since the logical device can not be expanded, the dynamic expansion option from the OpenVMS side would be useless.

It's been three years so a lot could have changed but I distinctly remembering that this was a function that was possible on Windows (the ACU had an option for it) but not possible for OpenVMS.

For what it's worth...
Volker Halle
Honored Contributor

Re: Expanding a RAID-5 array

Keith,

the Smart Array 5300 User Guide is dated from May 2002. OpenVMS V7.3-2, which supportes DVE (Dynamic Volume Expansion) has been released in August 2002.

The Smart Array seems to be able to 'expand' arrays and 'extend' logical volumes (on those arrays).

OpenVMS only sees the logical volume and if the OpenVMS volume had been initialized with a big-enough volume expansion size, you can increase the useable size on the volume (SET VOL/SIZE). If not, you have to use SET VOL/LIMIT (after mounting the disk privately) first.

Note that the Smart array manual 'suggests' a full backup before these operations.

I see a good chance, that this will work with OpenVMS Alpha V8.3.

Volker.
Volker Halle
Honored Contributor

Re: Expanding a RAID-5 array

but...

The Array Configuration Utility available for Tru64 UNIX and OpenVMS are ports of the ACU-XE utility utilized on ProLiant servers. Note that the Volume Extension function provided by the ACU-XE utility for the Smart Array 6400 on ProLiant servers is not enabled in the Tru64 UNIX and OpenVMS versions of the ACU-XE utility.

from:

http://h18002.www1.hp.com/alphaserver/products/storage/sa5300a/sa5300a_qa.html

Volker.
Volker Halle
Honored Contributor

Re: Expanding a RAID-5 array

Keith,

MSA$UTIL seems to support /EXTEND and /EXPAND qualifiers, so this may be a way to go. See the V8.3-1H1 Relese Notes.

Volker.