Hello Pierre, thank You for these useful test commands. Here is what I did: Pierre Frédéric Caillaud: > Try this : > > CREATE TABLE test AS SELECT * FROM yourtable; > > This will test write speed, and TOAST compression speed. > Then try this: (1) Setting: * pg_xlog sym'linked to another disk (to "system disk") * having approx 11.1 GB in 'yourtable' on "data disk" * executed SQL by pgAdmin III (as above, no transaction) Speed: * 754 s (14.5 MB/s) > CREATE TABLE test (LIKE yourtable); > COMMIT; > INSERT INTO test SELECT * FROM yourtable; > > This does the same thing but also writes WAL. > I wonder what results you'll get. (2) Setting: like (1), and 'test' table removed first Speed: 752 s (so, the same since pg_xlog sym'linked) (3) Setting: like (2), but removed symlink of pg_xlog, so having it again on "data disk" where big data is Speed: 801 s (so ~1 minute longer) BTW: I expected longer duration for scenario (3). IMHO: As neither the CPUs nor the disk throughput nor the postgres.exe task's CPU consumption was at its limits: I wonder what is the problem here. Maybe it is not postgresql related at all. I'll try to execute these tests on a SSD and/or Raid system. Felix -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
