Re: SSD + RAID

From: Greg Smith <greg(at)2ndquadrant(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>, pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: SSD + RAID
Date: 2010-02-27 19:38:20
Message-ID: 4B8974AC.9010609@2ndquadrant.com
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Bruce Momjian wrote:
> I have added documentation about the ATAPI drive flush command, and the
> typical SSD behavior.
>

If one of us goes back into that section one day to edit again it might
be worth mentioning that FLUSH CACHE EXT is the actual ATAPI-6 command
that a drive needs to support properly. I wouldn't bother with another
doc edit commit just for that specific part though, pretty obscure.

I find it kind of funny how many discussions run in parallel about even
really detailed technical implementation details around the world. For
example, doesn't
http://www.mail-archive.com/zfs-discuss(at)opensolaris(dot)org/msg30585.html
look exactly like the exchange between myself and Arjen the other day,
referencing the same AnandTech page?

Could be worse; one of us could be the poor sap at
http://opensolaris.org/jive/thread.jspa;jsessionid=41B679C30D136C059E1BB7C06CA7DCE0?messageID=397730
who installed Windows XP, VirtualBox for Windows, an OpenSolaris VM
inside of it, and then was shocked that cache flushes didn't make their
way all the way through that chain and had his 10TB ZFS pool corrupted
as a result. Hurray for virtualization!

--
Greg Smith 2ndQuadrant US Baltimore, MD
PostgreSQL Training, Services and Support
greg(at)2ndQuadrant(dot)com www.2ndQuadrant.us

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