I have some data here, no detailed analyses though:



On Mon, Nov 08, 2004 at 01:26:09PM +0100, Dawid Kuroczko wrote:
> The ext3fs allows to selet type of journalling to be used with
> filesystem.  Journalling pretty much "mirrors" the work of WAL
> logging by PostgreSQL...  I wonder which type of journalling
> is best for PgSQL in terms of performance.
> Choices include:
>               journal
>                      All data is committed into the  journal  prior  to  being
>                      written into the main file system.
>               ordered
>                      This  is  the  default mode.  All data is forced directly
>                      out to the main file system prior to its  metadata  being
>                      committed to the journal.
>               writeback
>                      Data ordering is not preserved - data may be written into
>                      the main file system after its metadata has been  commit-
>                      ted  to the journal.  This is rumoured to be the highest-
>                      throughput option.  It guarantees  internal  file  system
>                      integrity,  however  it  can  allow old data to appear in
>                      files after a crash and journal recovery.
> Am I right to assume that "writeback" is both fastest and at the same
> time as safe to use as ordered?  Maybe any of you did some benchmarks?
> Regards,
>      Dawid

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