Hi, at the moment we encounter some performance problems with our database server. We have a 12 GB RAM machine with intel i7-975 and using 3 disks "Seagate Barracuda 7200.11, ST31500341AS (1.5 GB)" One disk for the system and WAL etc. and one SW RAID-0 with two disks for postgresql data. Our database is about 24GB. Our munin graph reports at 9:00 a clock writes of 3000 blocks per second and reads of about 1000 blocks per second on our disk which holds the data directories of postgresql (WAL are on a different disk) 3000 blocks ~ about 3 MB/s write 1000 blocks ~ about 1 MB/s read At the same time we have nearly 50% CPU I/O wait and only 12% user CPU load (so 4 of 8 cpu cores are in use for io wait) We know, its a poor man disk setup (but we can not find a hoster with rather advanced disk configuration at an affordable price). Anyway, we ran some tests on it: # time sh -c "dd if=/dev/zero of=bigfile bs=8k count=3000000 && sync" 3000000+0 records in 3000000+0 records out 24576000000 bytes (25 GB) copied, 276.03 s, 89.0 MB/s real 4m48.658s user 0m0.580s sys 0m51.579s # time dd if=bigfile of=/dev/null bs=8k 3000000+0 records in 3000000+0 records out 24576000000 bytes (25 GB) copied, 222.841 s, 110 MB/s real 3m42.879s user 0m0.468s sys 0m18.721s Of course, writing large chunks is quite a different usage pattern. But I am wondering that writing 3MB/s and reading 1 MB/s seams to be a limit if i can run a test with 89 MB/s writing and 110MB/s reading. Can you give some hints, if this numbers seems to be reasonable? kind regards Janning -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
