On Thu, Jun 6, 2013 at 9:53 AM, Ray Cote <rgac...@appropriatesolutions.com>wrote:
> 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%. > > When I'm not writing to the database, it becomes quiet without any disk > activity. > > This is a 256 MByte system and atop shows we're not swapping > Is autovacuum set to 'on'? Possibly there is bloat in your table and indexes; what happens to the system after you issue a manual "VACUUM ANALYZE VERBOSE"? If that helps, you might need to make your autovacuum settings more aggressive.
