From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Doug McNaught <doug(at)wireboard(dot)com> |
Cc: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Greg Copeland <greg(at)copelandconsulting(dot)net>, shridhar_daithankar(at)persistent(dot)co(dot)in, PostgresSQL Hackers Mailing List <pgsql-hackers(at)postgresql(dot)org>, PostgresSQL General Mailing List <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: [HACKERS] Performance while loading data and indexing |
Date: | 2002-09-27 03:07:44 |
Message-ID: | 20359.1033096064@sss.pgh.pa.us |
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Lists: | pgsql-general pgsql-hackers pgsql-performance |
Doug McNaught <doug(at)wireboard(dot)com> writes:
> "data=writeback" means that no data is journaled, just metadata (which
> is like XFS or Reiser). An fsync() call should still do what it
> normally does, commit the writes to disk before returning.
> "data=journal" journals all data and is the slowest and safest.
> "data=ordered" writes out data blocks before committing a journal
> transaction, which is faster than full data journaling (since data
> doesn't get written twice) and almost as safe. "data=writeback" is
> noted to keep obsolete data in the case of some crashes (since the
> data may not have been written yet) but a completed fsync() should
> ensure that the data is valid.
Thanks for the explanation.
> So I guess I'd probably use data=ordered for an all-on-one-fs
> installation, and data=writeback for a WAL-only drive.
Actually I think the ideal thing for Postgres would be data=writeback
for both data and WAL drives. We can handle loss of un-fsync'd data
for ourselves in both cases.
Of course, if you keep anything besides Postgres data files on a
partition, you'd possibly want the more secure settings.
regards, tom lane
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