From: Albert Cervera Areny <albert@sedifa.com>
To: pgsql-performance@postgresql.org
Subject: Bad RAID1 read performance
Date: Wed, 30 May 2007 11:35:32 +0200
Message-ID: <200705301135.32236.albert@sedifa.com> (raw)
Hi,
after doing the "dd" tests for a server we have at work I obtained:
Read: 47.20 Mb/s
Write: 39.82 Mb/s
Some days ago read performance was around 20Mb/s due to no readahead in md0
so I modified it using hdparm. However, it seems to me that being it a RAID1
read speed could be much better. These are SATA disks with 3Gb of RAM so I
did 'time bash -c "dd if=/dev/zero of=bigfile bs=8k count=786432 && sync"'.
File system is ext3 (if read many times in the list that XFS is faster), but
I don't want to change the file system right now. Modifing the readahead from
the current 1024k to 2048k doesn't make any difference. Are there any other
tweaks I can make?
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To: pgsql-performance@postgresql.org
Cc: albert@sedifa.com
Subject: Re: Bad RAID1 read performance
In-Reply-To: <200705301135.32236.albert@sedifa.com>
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