Thanks everyone. You have helped back up my suspicions. It is indeed a Linux system, and it has a RAID IO system, but I don't yet know the details of that IO system. Time to put them back to work looking at their hardware, rather than blaming our software :) Thanks for the extra tips on hunting for excess IO from other processes. Dan -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general