Re: Load distributed checkpoint

From: "Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
To: "Inaam Rana" <inaamrana(at)gmail(dot)com>
Cc: "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Load distributed checkpoint
Date: 2006-12-26 03:13:44
Message-ID: 027701c7289b$d9f0fe40$19527c0a@OPERAO
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Hello, Inaam-san,

> There are four IO schedulers in Linux. Anticipatory, CFQ (default),
deadline, and noop. For typical OLTP type loads generally deadline is
recommended. If you are constrained on CPU and you have a good controller
then its better to use noop.
> Deadline attempts to merge requests by maintaining two red black trees in
sector sort order and it also ensures that a request is serviced in given
time by using FIFO. I don't expect it to do the magic but was wondering that
it may dilute the issue of fsync() elbowing out WAL writes.
> You can look into /sys/block/<device>/queue/scheduler to see which
scheduler you are using.

Thank you for your information.
I could only find the following files in /sys/block/<device>/queue/:

iosched
max_hw_sectors_kb
max_sectors_kb
nr_requests
read_ahead_kb

In iosched, the following files exist:

quantum (the content is "4")
queued (the content is "8")

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