MS wrote:
Btw. It looks like this issue: http://archives.postgresql.org/pgsql-performance/2007-09/msg00374.php In my case the CPU usage is low too (3%) but IO wait is high (95%). I'm using Postgresql 8.3.
for more info on disk iowaits, use `iostat -x 5` (5 means sample every 5 seconds), and ignore the first sample as its the average system system boot. this will give you drive by drive and flie system by file system details of disk IO. The exact details shown vary by operating system.
note, on many linux distributions, iostat is part of the sysstat package, which often isn't installed by default especailly on a 'minimum' install... on RH/Fedora/Centos type systems, try `yum install sysstat` to install it.
I never cease to be amazed at how many times people have these monster CPUs, like dual quad core 3Ghz processors, with 16GB or whatever of ram, and then try and run a database off a single 7200 rpm desktop SATA drive. at work our production databases often run on dozens of 10000 or 15000 rpm drives, organized as raid1+0's.
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