Oracle-L: Re: Sizing - RAC, storage subsystem EMC

From: Binley Lim <Binley.Lim_at_xtra.co.nz>
Date: Thu, 22 May 2003 12:42:59 -0800
Message-ID: <F001.005A0A13.20030522124259@fatcity.com>

This message refers to SAN, but NetApps are happy to recommend a large number (>10) for their RAID-4 NAS as well.

The NAS vendor say you can "carry on" during the resync, but I suspect very few souls will do this if they can help it. If you choose to "carry on", detection of any potential failure of a second disk "will stop the storage server".

As an optimist, I would like to believe the storage vendors can get things right. I would rather not spend time on I/O distribution across individual mountpoints/spindles/small-volumes. Let the storage vendors take care of such details.

Original Message ----- From: Cary Millsap To: Multiple recipients of list ORACLE-L Sent: Friday, May 23, 2003 4:42 AM Subject: RE: Sizing - RAC, storage subsystem EMC

Oh man, .One parity disk for 10-20 disks means that if *any* single disk in the group fails (which will happen five times more frequently in a 20-drive group than in a 4-drive group), then for the duration of the partial outage every single read from the failed disk is going to engage all 10-20 disks in the group. And the resynchronization of the new disk, once it's plugged in, is going to require the *full disk scan of all 10-20 devices*. I wouldn't want to be anywhere nearby when *that* happened.

  Cary Millsap
  Hotsos Enterprises, Ltd.
  http://www.hotsos.com

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Author: Binley Lim
INET: Binley.Lim_at_xtra.co.nz

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