RE: Write cache for a SAN
- From: "Bobak, Mark" <Mark.Bobak@xxxxxxxxxxxx>
- To: "jkstill@xxxxxxxxx" <jkstill@xxxxxxxxx>, "dofreeman@xxxxxxxxxxx" <dofreeman@xxxxxxxxxxx>
- Date: Mon, 3 Nov 2008 14:29:10 -0500
Jared,
We actually suffered a "SANtastrophe" about three years ago, in a real life
circumstance that was quite similar to the one you describe.
The way the story was told to me, the SAN frame has a redundant power supply,
and one of the two power supplies went bad, and the unit phoned home. EMC tech
shows up w/ replacement power supply in hand, a few hours later. (This is the
way it's supposed to work, right?) Well, apparently, he pulled the good power
supply, rather than the bad power supply....leaving the frame to come crashing
down w/ no power.....oops.....
36 hours, and about 2.5TB restored from tape later, and we were back in
business.
This really is the exception, though, and not the rule. I don't think
disabling write caching is the right move. Ultimately, at some point, you have
to have some faith in the hardware you've got and the people you work with.
-Mark
--
Mark J. Bobak
Senior Database Administrator, System & Product Technologies
ProQuest
789 E. Eisenhower, Parkway, P.O. Box 1346
Ann Arbor MI 48106-1346
+1.734.997.4059 or +1.800.521.0600 x 4059
mark.bobak@xxxxxxxxxxxx<mailto:mark.bobak@xxxxxxxxxxxxxxx>
www.proquest.com<http://www.proquest.com>
www.csa.com<http://www.csa.com>
ProQuest...Start here.
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Jared Still
Sent: Monday, November 03, 2008 2:09 PM
To: dofreeman@xxxxxxxxxxx
Cc: Oracle-L Freelists
Subject: Re: Write cache for a SAN
On Mon, Nov 3, 2008 at 7:19 AM, Freeman, Donald
<dofreeman@xxxxxxxxxxx<mailto:dofreeman@xxxxxxxxxxx>> wrote:
We don't disable it. The SAN manufacturers have made this as bullet proof as
possible.
Guess what happens when the storage vendor sends out a tech to replace batteries
(the batteries that ensure the write cache stays put), and the tech can't be
bothered
to follow instructions?
What do you think might happen to the write cache?
I'm not saying that the write cache should be disabled, but you need to ensure
that
the folks that maintain the HW actually know what they are doing.
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
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