topic Re: Raid Software upgrade in Operating System - OpenVMS

Raid Software upgrade

Johan Eklund_1 — Thu, 01 Dec 2005 11:46:39 GMT

Hi,

I'm about to upgrade an Alpha system running VMS V7.2-1H1 to V7.3-2. The Raid version is old, V2.3 and I intend to go to Raid V3.0 after upgrading VMS. Disks attached to HSZ-70s running lastest and greatest V7.7.
Now, does anybody have any special ideas, hints, thoughts or warnings about this?

Best regards
Johan

Re: Raid Software upgrade

Ian Miller. — Thu, 01 Dec 2005 12:52:43 GMT

The Raid you are referring to is
the software raid software that runs runs on VMS? Is V2.3 qualified for V7.3-2 ? If not parhaps you can remove it from the startup until you perform the upgrade to V3.

I have seen no problems with HSZ70 firmware V7.7 and VMS V7.3-2.

Re: Raid Software upgrade

Kris Clippeleyr — Thu, 01 Dec 2005 14:35:35 GMT

Johan,
Maybe not an option in your case, but wouldn't it be better to let the RAIDing be done by the HSZ instead of by software. In my experience the HSZs do a pretty good job especially at RAID 5.
Regards,
Kris (aka Qkcl)

Re: Raid Software upgrade

Jan van den Ende — Thu, 01 Dec 2005 15:11:41 GMT

Johan,

I have to second Kris on that!.
We have been using HSZs fully to satisfaction for nearly a decade (until they got replaced by SAN).

hth.

Proost.

Have one on me.

jpe

Re: Raid Software upgrade

Johan Eklund_1 — Fri, 02 Dec 2005 01:43:23 GMT

Hi!

Thanx all for your input. Ian was touching on the part that concerns me, not very much but anyhow. Raid V2.3 is very old and it is not supported [on anything ;-)]. We are heading for V3.0 and, when upgrading I do want to be certain that I do not run into any "incompatibility"-problems when upgrading the Raidsets. Backups will be taken of course but they are quite a few those Raidsets and time might be crucial if I would have to restore all of them.

/Johan

Re: Raid Software upgrade

Ian Miller. — Fri, 02 Dec 2005 04:59:54 GMT

Looking at this
http://h71000.www7.hp.com/openvms/os/swroll/73-2.HTML

RAID V2.3 is too old for V7.3-2

Re: Raid Software upgrade

Galen Tackett — Mon, 05 Dec 2005 07:26:55 GMT

There is room for problems to occur here. At my previous job we tripped over several bugs over time as new versions of RAID software were released, starting around RAID V2.3 "dash something".

After installing one of these, when you replaced a failed drive with a drive of the same size but different geometry, they weren't treated as equivalent due to some miscalculation based on geometry. This was fixed in the next release.

Another problem arose when we updated a DS25 from VMS V7.3-1 to V7.3-2, back when V7.3-2 was pretty new. After the upgrade, every time we started up the RAID software the system would crash. I think the fix for this has also made its way into subsequent releases.

Dieter Froehlin of HP quickly supplied us with engineering patches before the new releases became available. I commend him.

Re: Raid Software upgrade

Johan Eklund_1 — Mon, 12 Dec 2005 11:15:27 GMT

Hi again,

It all went well although we did have som problems but no real show-stoppers. So, I just wanted to thank you all for your interest.

regards
Johan

Re: Raid Software upgrade

Johan Eklund_1 — Mon, 12 Dec 2005 11:16:39 GMT

Bye for now

Re: Raid Software upgrade

Keith Parris — Mon, 12 Dec 2005 20:16:26 GMT

Kris wrote: "Wouldn't it be better to let the RAIDing be done by the HSZ instead of by software? In my experience the HSZs do a pretty good job, especially at RAID 5."

Although the original design intent of the HP (formerly StorageWorks) RAID Software for OpenVMS was to do RAID-5 in host software (and it accomplished that about a year before controllers which could do it in firmware/hardware became available), and it could provide RAID-5 protection for plain, ordinary local disks which weren't behind an expensive array controller, eventually array controllers with RAID became readily available and relatively inexpensive, and a host-based product incurs the overhead of extra I/Os required to update parity metadata so as to cover the "write hole" in RAID-5 writes (extra I/Os which weren't needed in controller [pair]s with mirrored non-volatile write-back cache which could be used to hold RAID-5 metadata during writes) and this hurt host-based RAID-5 performance, so use of the product for RAID-5 has tended to decrease over time.

But RAID-0 (disk striping) capabilities were added to the product along the way, so in fact today the most common use in practice for the product is to do disk striping (RAID-0) or RAID 0+1 (stripesets of shadowsets). This allows I/O workload to be spread across multiple controllers, so that I/O loads can be handled which are greater than any single controller can handle.

Some customers use the software to combine a number of relatively smaller disk volumes (which can all shadow-copy in parallel, each with their own copy thread, and thus complete faster) into larger volumes for use by VMS or applications.

It also has the capability of doing partitioning (either of an array of disks, or even of a single individual disk), for folks who need that capability on VMS.