I have a PostgreSQL 9.0.3 database that has suddenly started exhibiting odd read behavior.
The version number is: "PostgreSQL 9.0.3 on x86_64-unknown-linux-gnu, compiled by GCC gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-50), 64-bit" This was compiled from source about a year ago and has been running just fine. The database feeds a very low-volume web site (a few hits per minute).
Starting a few days ago we started to see a strange behavior where writing to the database causes massive read operations. For example, I have a table that needs to be updated every night (about 20,000 rows). Using Django ORM, we update them one item at a time. Usually the overall process takes a few minutes; it is now taking hours (like over 15 hours).
Running atop, we're seeing Read Disk values in the range of 147.2M/10s and Write Disk values in the range of 16K/10s. Together, the Disk throughput is in the high 90% and frequently hits 100%.
Which specific processes are using the disk? (on my atop, if I hit 'c' it will change mode to show me the entire so-called "command line", which will let you know if the culprit is a vacuum worker, the checkpointer, or someone else).
