On Thu, 26 Apr 2007, Zeugswetter Andreas ADI SD wrote:

I am not sure that shrinking per WAL record size (other than the full
page images), e.g. by only logging changed bytes and not whole tuples,
would have a huge impact on OLTP tx/sec, since the limiting factor is
IO's per second and not Mb per second.

With the kind of caching controller that's necessary for any serious OLTP work with Postgres, number of I/Os per second isn't really an important number. Total volume of writes to the WAL volume can be though. It's difficult but not impossible to encounter a workload that becomes bottlenecked by WAL volume on a good OLTP server, particularly because that's often going to a single or RAID-1 disk. Whether those workloads also have the appropriate properties such that their WAL could be shrunk usefully in real-time is a good question.

* Greg Smith [EMAIL PROTECTED] http://www.gregsmith.com Baltimore, MD

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