LRUS / page cleaner recommendations on 10.0?

What is the accepted wisdom for determining LRUS and CLEANERS on 10.0 running on RAID 1+0 ? I seem to be getting conflicting opinions from different sources. Andy

ANDY KENT wrote: > What is the accepted wisdom for determining LRUS and CLEANERS on 10.0 running > on RAID 1+0 ? I seem to be getting conflicting opinions from different > sources. > Andy, First, whatever you set LRUS (or the equivalent VPCLASS field) to set CLEANERS to at least the total of all LRUS settings across all buffer caches. This insures minimal checkpoint durations. LRUS configuration is tricky. There's no good rule of thumb. You need to set it high enough that sessions don't contend for LRU queues. That's mostly a function of the number of concurrent active users on the system and the update mix. More users modifying the buffer cache require more LRUs to spread the load out. Partly it's based on luck - sessions select an LRU queue when they need to read data into the cache from disk more or less randomly based in part on their session id. Paul Watson feels that always setting LRUS to maximum (128 or 256 depending on 32bit or 64 bit) is harmless and relieves that one tuning burden. On the other hand we have one client with up to 1400 connections at a time that runs with 16 LRUs and their BR (Bufwaits Ratio) values are consistently below 3.00. On the random luck side, if you see that your LRUs are being used unevenly (onstat -R always shows the same LRUS with the most dirty pages) increasing or reducing the number by one can sometimes have a dramatic effect by changing the hash that selects which LRU to use next. Select a likely setting and monitor the BR of the server over time and adjust as needed to get your BR below 7.0. Art S. Kagel > Andy > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > See you at the IIUG Informix 2008 Conference > The Power Conference for Informix Professionals > April 27 - 30, 2008 Marriott Overland Park (Kansas City), Kansas > http://www.iiug.org/conf > Registration Now Open!! > > ================================================================================ =========== > Please access the attached hyperlink for an important electronic communications disclaimer: > > http://www.oninit.com/home/disclaimer.php > > ================================================================================ =========== > > > ================================================================================ =========== Please access the attached hyperlink for an important electronic communications disclaimer: http://www.oninit.com/home/disclaimer.php ================================================================================ ===========