Greg - Thanks for the heads up. The box in question is a dual cpu (xeon dual cores) with 8 gig & a pair of 10k 146gb raid 1 arrays. I have the pg_xlog dir on one array (along with the OS) & the rest of the data on the other array by itself. Given that this is a production system I'm going to tone things down a bit as you suggested prior to the open today. While I don't like the 10-20 second pauses every 5 minutes it's a system I need to have running and I'd rather not take the chance of bringing the system to its knees. A couple of quick questions. On the fly I can change these params and use 'pg_ctl reload" to put them in effect, correct? That way I can play a little today and see what the effects are. Also, I have my checkpoint_segments set to 10, if I were to lower this (say 5) would this possible have the effect of checkpointing a little more often with less data? (right now I hit the checkpoint_timeout). Thanks again, Marc ----- Original Message ---- From: Greg Smith <gsmith@xxxxxxxxxxxxx> To: Marc Rossi <marc_rossi@xxxxxxxxx> Cc: pgsql-general@xxxxxxxxxxxxxx Sent: Friday, August 10, 2007 2:36:28 AM Subject: Re: UPDATES hang every 5 minutes On Thu, 9 Aug 2007, Marc Rossi wrote: > as well as made changes to the bgwriter settings as shown below (taken > from a post in the pgsql-performance list) >bgwriter_lru_percent = 20.0 # 0-100% of LRU buffers scanned/round >bgwriter_lru_maxpages = 200 # 0-1000 buffers max written/round >bgwriter_all_percent = 10.0 # 0-100% of all buffers scanned/round >bgwriter_all_maxpages = 600 # 0-1000 buffers max written/round Be warned that these are settings from a much more powerful server than it sounds like you have, and I wouldn't be surprised to find your average performance tanks as a result. Making the background writer this aggressive will waste a lot of I/O, and unless you've got a lot of spare I/O to waste (which was the case on the source of this tuning) it can make your problem worse. I'd hesitate to recommend setting either percentage over 5% or either maxpages>100 as a first step on a production system. You may be in for a bad day tomorrow. -- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
