On Thu, 9 Oct 2003, Bruce Momjian wrote: > scott.marlowe wrote: > > I was testing to get some idea of how to speed up the speed of pgbench > > with IDE drives and the write caching turned off in Linux (i.e. hdparm -W0 > > /dev/hdx). > > > > The only parameter that seems to make a noticeable difference was setting > > wal_sync_method = open_sync. With it set to either fsync, or fdatasync, > > the speed with pgbench -c 5 -t 1000 ran from 11 to 17 tps. With open_sync > > it jumped to the range of 45 to 52 tps. with write cache on I was getting > > 280 to 320 tps. so, not instead of being 20 to 30 times slower, I'm only > > about 5 times slower, much better. > > > > Now I'm off to start a "pgbench -c 10 -t 10000" and pull the power cord > > and see if the data gets corrupted with write caching turned on, i.e. do > > my hard drives have the ability to write at least some of their cache > > during spin down. > > Is this a reason we should switch to open_sync as a default, if it is > availble, rather than fsync? I think we are doing a single write before > fsync a lot more often than we are doing multiple writes before fsync.
Sounds reasonable to me. Are there many / any scenarios where a plain fsync would be faster than open_sync? ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org