Disk Performance Problem on Large DB

Hello,

I have a RHEL 5 box, 4 GB RAM, single hard drive SATA, Intel Core 2 Duo 2.4. A basic workstation.

I have a simple database, with one table for now. It has 4 columns:

anid serial primary key unique,
time timestamp,
source varchar(5),
unitid varchar(15),
guid varchar(32)

There is a btree index on each.

I am loading data 1,000,000 (1M) rows at a time using psql and a COPY command. Once I hit 2M rows, my performance just drops out, and the next 1M never finishes. It takes 7 minutes for 1M rows to load. Once 2M are in there, I've waited an hour, and nothing. It doesn't seem to matter which 1M rows I try to load next, none ever finish. Each 1M rows is about 70MB on disk in the raw input file.

I have "atop" installed, and it reports the drives at 100%, which it reports for the first 1M rows too. The MBw/s goes from 20+ on the first 2M rows, down to about 4 MBw/s or less now. The processor usage is at about 2 to 8% at this time (used by postgres).

I have even waited for 1M rows to load, then done a vacuum for no good reason, then even restarted postgresql. I've made sure no disk or proc activity is happening before I start the next 1M rows. None of that seems to matter.

I have a total of about 70M rows to load, but am at a standstill. I've read up on whatever performance docs I can find online, but I am not getting anywhere.

I've increased shared_buffers to 256MB, and I've tried it with fsync commented out as per the default config. I've also tried it with fsync=off. No difference.

Ideas? Thanks in advance,
Jon