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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 01:40:31
Message-ID: 3f0b79eb1002171740y2379a16aw4e25852bb9c3c87c@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Thu, Feb 18, 2010 at 5:28 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> If I'm reading the patch correctly, when wal_sync_method is 'open_sync',
> walreceiver nevertheless opens the WAL file without the O_DIRECT flag.
> When it later flushes it in XLogWalRcvFlush() by issue_xlog_fsync(),
> issue_xlog_fsync() will do nothing because it assumes the write() synced
> it already. So the data written isn't being forced to disk at all.

When 'open_sync' is chosen, the WAL file is opened with O_SYNC or O_FSYNC
flag. So I think that write() flushes the data to disk even if O_DIRECT
flag is not given. Am I missing something?

> How about just forcing sync_method to 'fsync' in walreceiver?

In win32, O_DSYNC seems to be preferred to 'fsync' so far. So I'm not sure
if reshuffling of priority is harmless.
http://archives.postgresql.org/pgsql-hackers-win32/2005-03/msg00148.php

Regards,

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

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