Re: Load distributed checkpoint

Happy new year

From: "Simon Riggs" <simon@2ndquadrant.com>
> Have you tried setting deadline scheduler on the WAL device and CFQ
on
> the data device? That should allow the I/Os to move through
different
> queues and prevent interference.

No, I've not tried yet.  Inaam-san told me that Linux had a few I/O
schedulers but I'm not familiar with them.  I'll find information
about them (how to change the scheduler settings) and try the same
test.


----- Original Message ----- 
From: "Simon Riggs" <simon@2ndquadrant.com>
To: "Takayuki Tsunakawa" <tsunakawa.takay@jp.fujitsu.com>
Cc: "ITAGAKI Takahiro" <itagaki.takahiro@oss.ntt.co.jp>;
<pgsql-hackers@postgresql.org>
Sent: Thursday, December 28, 2006 7:07 AM
Subject: Re: [HACKERS] Load distributed checkpoint


> On Mon, 2006-12-18 at 14:47 +0900, Takayuki Tsunakawa wrote:
>> Hello, Itagaki-san, all
>>
>> Sorry for my long mail.  I've had trouble in sending this mail
because
>> it's too long for pgsql-hackers to accept (I couldn't find how
large
>> mail is accepted.)  So I'm trying to send several times.
>> Please see the attachment for the content.
>
> Your results for fsync are interesting.
>
> I've noticed that a checkpoint seems to increase the activity on the
WAL
> drive as well as increasing I/O wait times. That doesn't correspond
to
> any real increase in WAL traffic I'm aware of.
>
> Have you tried setting deadline scheduler on the WAL device and CFQ
on
> the data device? That should allow the I/Os to move through
different
> queues and prevent interference.
>
> -- 
>  Simon Riggs
>  EnterpriseDB   http://www.enterprisedb.com
>
>
>