Re: raid 5 disaster

From: Jared Still <jkstill_at_cybcon.com>
Date: Sat, 14 Aug 2004 08:28:17 -0700
Message-Id: <1092497296.13647.23.camel@poirot>

On Sat, 2004-08-14 at 07:05, Mogens NÃ¸rgaard wrote:

> Since this was the old Shark, we knew it was using cheap, slow, old
> disks (7500 RPM). And 8-pack contains 6 data disks, one dedicated parity
> disk (RAID-4) and one hot spare. So a total of 300 IO's per second per
> 8-pack was to be expected.
>

We purchased this same system several year ago at a previous employer.

When I sat down with the IBM technical consultant, I was somewhat aghast to learn of this configuration. But, it was actually worse than you have portrayed it.

There were 4x8 packs in this system, and they could not all be configured the same way. Two of them were allowed to have one less disk dedicated to overhead, which created some very odd stripe sizes.

It wasn't bad enough that the only configuration available was RAID-4/5. I wasn't impressed. The Sharks didn't go into production until after I left the company, but I was told by a project mgr on the DW project the performance was indeed less than stellar.

BAARF! Wish I had had my 'No RAID5' hat then.

Jared

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Received on Sat Aug 14 2004 - 10:23:05 CDT