-------- Original Message --------
Subject: [zfs-discuss] MySQL benchmark
Date: Tue, 30 Oct 2007 00:32:43 +0000
From: Robert Milkowski <rmilkowski at task.gda.pl>
Reply-To: Robert Milkowski <rmilkowski at task.gda.pl>
Organization: CI TASK http://www.task.gda.pl
To: zfs-discuss at opensolaris.org
Hello zfs-discuss,
http://dev.mysql.com/tech-resources/articles/mysql-zfs.html
I''ve just quickly glanced thru it.
However the argument about double buffering problem is not valid.
--
Best regards,
Robert Milkowski mailto:rmilkowski at task.gda.pl
http://milek.blogspot.com
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I absolutely agree with Robert here. Data is cached once in the
Database and, absent directio, _some_ extra memory is required
to stage the I/Os. On read it''s a tiny amount since memory
can be reclaimed as soon as it''s copied to user space.
10000 threads each waiting for 8K will serviced using 80M
of extra memory.
On the write path we need to stage the data for the purpose
of a ZFS transaction group. When the dust settles we will be
able to do this every 5 seconds. So what percentage of
DB blocks are modified in 5 to 10 seconds ?
If the answer is >5% then yes, the lack of directio is a
concern for you.
-r