| From: | "Jim C(dot) Nasby" <decibel(at)decibel(dot)org> |
|---|---|
| To: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
| Cc: | Dimitri <dimitrik(dot)fr(at)gmail(dot)com>, PostgreSQL Performance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Filesystem Direct I/O and WAL sync option |
| Date: | 2007-07-09 20:32:20 |
| Message-ID: | 20070709203220.GO39272@nasby.net |
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| Lists: | pgsql-performance |
On Tue, Jul 03, 2007 at 04:06:29PM +0100, Heikki Linnakangas 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.
BTW, it might be worth trying the different wal_sync_methods. IIRC,
Jonah's seen some good results from open_datasync.
--
Jim Nasby decibel(at)decibel(dot)org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)
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