Re: [Veritas-bu] Destaging going slow

Of course with the advent of SSD drives its quite possible (I’d say probable) that over time the price will come down and rather than going to a new triple parity RAID we’ll probably end up using nothing but SSD for performance. The “rebuild” of an SSD would be orders of magnitude faster than of a mech drive. A triple parity RAID might eventually be needed even so but I’m guessing that would be many years in the future.

So far (knock wood) I’ve not seen a triple failure in over 5 years so RAID 10 still seems to do the job for us from a stability point of view.

From: veritas-bu-bounces AT mailman.eng.auburn DOT edu [mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Matteson, Ryan
Sent: Tuesday, July 13, 2010 9:52 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Destaging going slow

We just suffered a double disk failure in a well-known commercial SATA storage array last weekend (sucks we were using RAID5). After recovering all of our data from tape, we have since moved the system to RAID6. Adam Leventhal has a great paper on this topic:

http://queue.acm.org/detail.cfm?id=1670144

And I would highly recommended reading it.

- Ryan

From: veritas-bu-bounces AT mailman.eng.auburn DOT edu [mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Lightner, Jeff
Sent: Tuesday, June 29, 2010 10:53 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Destaging going slow

When I first got to this job we had a major outage of multiple environments because they’d all been built on a single RAID5 array that had a second disk fail while rebuilding the first disk that had failed. RAID10 will survive double disk failure. If you must do RAID5 make it into discreet sets so that the amount you lose in double-disk failure is manageable.

From: veritas-bu-bounces AT mailman.eng.auburn DOT edu [mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Ed Wilts
Sent: Tuesday, June 29, 2010 10:09 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] Destaging going slow

From a storage perspective, I've got all disks in a Dell MD1000 enclosure configured in a single 15 disk RAID-5.

Don't ever do this. Jonathan has obviously gotten away with this (so far) but using large drives (e.g. 1TB) in a 15-member RAID-5 set is just asking to lose the array due to a double-disk failure.

I've done several recoveries for our Windows Server Team because they're configured large RAID-5 sets and had double-disk failures.

../Ed

Ed Wilts, RHCE, BCFP, BCSD, SCSP, SCSE
ewilts AT ewilts DOT org

Proud partner. Susan G. Komen for the Cure.

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