On Mon, May 17, 2010 at 2:10 AM, Scott Marlowe <scott.marlowe@xxxxxxxxx> wrote: > On Mon, May 17, 2010 at 2:06 AM, Piotr Legiecki <piotrlg@xxxxxxxxxx> wrote: >> 2. select count(*) from some_table; runs in a fraction of a second on the >> console on both servers (there are only 4000 records, the second longer >> table has 50000 but it does not matter very much). From pg_admin the results >> are: >> - slow server (and the longest table in my db) 938ms (first run) and about >> 40ms next ones >> - fast server 110ms first run, about 30ms next ones. >> Well, finally my new server deservers its name ;-) The later times as I >> understand are just cache readings from postgresql itself? > SNIP >> So the server itself seems faster. >> So still I don't get this: select * from table; on old server takes 0,5 sec, >> on new one takes 6sec. Why there is so big difference? And it does not >> matter how good or bad select is to measure performance, because I don't >> measure the performance, I measure the relative difference. Somwhere there >> is a bottleneck. > > Yep, the network I'd say. How fast are things like scp between the > various machines? > >> 4. Machine. The new server has 5 SAS disks (+ 1 spare), but I don't remember >> how they are set up now (looks like mirror for system '/' and RAID5 for rest >> - including DB). size of the DB is 405MB > > Get off of RAID-5 if possible. A 3 Disk RAID-5 is the slowest > possible combination for RAID-5 and RAID-5 is generally the poorest > choice for a db server. I refer you to this classic post on the subject: http://www.mail-archive.com/pgsql-general@xxxxxxxxxxxxxx/msg93043.html -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
