Re: Filesystem Direct I/O and WAL sync option

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: Dimitri <dimitrik(dot)fr(at)gmail(dot)com>
Cc: PostgreSQL Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Filesystem Direct I/O and WAL sync option
Date: 2007-07-03 15:06:29
Message-ID: 468A65F5.8020800@enterprisedb.com
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Dimitri wrote:
> I'm very curious to know if we may expect or guarantee any data
> consistency with WAL sync=OFF but using file system mounted in Direct
> I/O mode (means every write() system call called by PG really writes
> to disk before return)...

You'd have to turn that mode on on the data drives as well to get
consistency, because fsync=off disables checkpoint fsyncs of the data
files as well.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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