Re: replication timeout in pg_basebackup

From: Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>
To: "Aggarwal, Ajay" <aaggarwal(at)verizon(dot)com>
Cc: "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org>
Subject: Re: replication timeout in pg_basebackup
Date: 2014-03-11 00:31:11
Message-ID: CAJrrPGdA99niTt96--MfC1851ayX_x3vS1VD=3-sb=HQ_PVarg@mail.gmail.com
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On Tue, Mar 11, 2014 at 7:07 AM, Aggarwal, Ajay <aaggarwal(at)verizon(dot)com> wrote:
> Thanks Hari Babu.
>
> I think what is happening is that my dirty cache builds up quickly for the
> volume where I am backing up. This would trigger flush of these dirty pages
> to the disk. While this flush is going on pg_basebackup tries to do fsync()
> on a received WAL file and gets blocked.

But the sync is executed for every WAL file finish. Does your database
is big in size?
Does your setup is write-heavy operations?

In Linux when it tries to write a bunch of buffers at once, the fysnc
call might block for some time.
In the following link there are some "Tuning Recommendations for
write-heavy operations" which might be useful to you.

http://www.westnet.com/~gsmith/content/linux-pdflush.htm

Any other ideas to handle these kind of problems?

Regards,
Hari Babu
Fujitsu Australia

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