From: Dimitri <dimitrik.fr@gmail.com>
To: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Filesystem Direct I/O and WAL sync option
Date: Tue, 3 Jul 2007 17:26:55 +0200
Message-ID: <5482c80a0707030826v38c59870ib90599ba43337e72@mail.gmail.com> (raw)
In-Reply-To: <468A65F5.8020800@enterprisedb.com>
References: <5482c80a0707030754o740c82b6s4598dc668720d014@mail.gmail.com>
<468A65F5.8020800@enterprisedb.com>
Yes, disk drives are also having cache disabled or having cache on
controllers and battery protected (in case of more high-level
storage) - but is it enough to expect data consistency?... (I was
surprised about checkpoint sync, but does it always calls write()
anyway? because in this way it should work without fsync)...
On 7/3/07, Heikki Linnakangas <heikki@enterprisedb.com> wrote:
> 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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To: pgsql-performance@postgresql.org
Cc: dimitrik.fr@gmail.com, heikki@enterprisedb.com
Subject: Re: Filesystem Direct I/O and WAL sync option
In-Reply-To: <5482c80a0707030826v38c59870ib90599ba43337e72@mail.gmail.com>
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