Gaetano Mendola wrote: > Hi all, > I started to do some performance tests (using pgbench) in order to > estimate the DRBD impact on our servers, my plan was to perform some > benchmarks without DRBD in order to compare the same benchmark with > DRBD. > I didn't perform yet the benchmark with DRBD and I'm already facing > something I can not explain (I performed at the moment only reads test). > > I'm using postgres 8.2.3 on Red Hat compiled with GCC 3.4.6. > > I'm using pgbench with scaling factor with a range [1:500], my server > has 4 cores so I'm trying with 16 client and 4000 transaction per > client: pgbench -t 4000 -c 16 -S db_perf. I did 3 session using 3 different > values of shared_buffers: 64MB, 256MB, 512MB and my server has 2GB. > > The following graph reports the results: > > http://img84.imageshack.us/my.php?image=totalid7.png > > as you can see using 64MB as value for shared_buffers I'm obtaining better > results. Is this something expected or I'm looking in the wrong direction? > I'm going to perform same tests without using the -S option in pgbench but > being a time expensive operation I would like to ear your opinion first.
I have complete today the other benchmarks using pgbench in write mode as well, and the following graph resumes the results: http://img440.imageshack.us/my.php?image=totalwbn0.png what I can say here the trend is the opposite seen on the read only mode as increasing the shared_buffers increases the TPS. I still didn't upgrade to 8.2.7 as suggested by Greg Smith because I would like to compare the results obtained till now with the new one (simulations running while I write) using postgres on a "DRBD partition"; sure as soon the current tests terminate I will upgrade postgres. If you have any suggestions on what you would like to see/know, just let me know. Regards Gaetano Mendola -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
