On Oct 13, 2006, at 17:35 , Andrew - Supernews wrote:
On 2006-10-13, Alexander Staubo <alex@xxxxxxxxxxxxxxx> wrote:
On Oct 13, 2006, at 17:13 , Andrew - Supernews wrote:
Your disk probably has write caching enabled. A 10krpm disk
should be
limiting you to under 170 transactions/sec with a single connection
and fsync enabled.
What formula did you use to get to that number?
It's just the number of disk revolutions per second. Without
caching, each
WAL flush tends to require a whole revolution unless the on-disk
layout of
the filesystem is _very_ strange. You can get multiple commits per WAL
flush if you have many concurrent connections, but with a single
connection
that doesn't apply.
Makes sense. However, in this case I was batching updates in
transactions and committing each txn at 1 second intervals, all on a
single connection. In other words, the bottleneck illustrated by this
test should not be related to fsyncs, and this does not seem to
explain the huge discrepancy between update (1,000/sec) and insert
(9,000 inserts/sec, also in 1-sec txns) performance.
Alexander.
