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Re: Streaming replication on win32, still broken

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Magnus Hagander <magnus(at)hagander(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Streaming replication on win32, still broken
Date: 2010-02-18 10:39:26
Message-ID: 3f0b79eb1002180239g2443e3b3qd8657c2662415c42@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, Feb 18, 2010 at 7:04 PM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> Magnus Hagander wrote:
>> O_DIRECT helps us when we're not going to read the file again, because
>> we don't waste cache on it. If we are, which is the case here, it
>> should be really bad for performance, since we actually have to do a
>> physical read.
>>
>> Incidentally, that should also apply to general WAL when archive_mdoe
>> is on. Do we optimize for that?
>
> Hmm, no we don't. We do take that into account so that we refrain from
> issuing posix_fadvice(DONTNEED) if archive_mode is on, but we don't
> disable O_DIRECT. Maybe we should..

Since the performance of WAL write is more important than that of WAL
archiving in general, that optimization might offer little benefit.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

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