On Thu, Aug 25, 2005 at 03:48:18PM +0100, Tony Finch said: > On Thu, 25 Aug 2005, Walt Reed wrote: > > On Thu, Aug 25, 2005 at 02:22:16PM +0100, Tony Finch said: > > > On Thu, 25 Aug 2005, Walt Reed wrote: > > > > > > > In addition to other suggestions that were put forth, making sure your > > > > RAID controller has battery backed write cache does AMAZING things for > > > > performance. > > > > > > And check the disk write caches are turned off :-) > > > > How so? I found the write cache sped most things up a LOT... Found it > > helped my database by a factor of 2. Added the cache on all my machines > > and overall load levels have dropped (as reported by MRTG. Especially > > the IOWait state.) > > If you have a battery-backed write cache on the controller, you don't need > or want a volatile write cache on the disks. The additional cache on the > disks will not improve performance and will reduce reliability. If the > disks lie to the controller about when data has hit stable storage then > the battery will not protect you from losing data in the event of a power > outage. > > http://www.livejournal.com/community/lj_dev/670215.html > http://www.livejournal.com/users/brad/2116715.html
Ahh. This is where the confusion was coming in. I was not talking about the cache on the physical disk. I was talking about the cache on the RAID controller. I was assuming that you were talking about the cache on the controller. Yes, disabling write cache on the disk itself IS a good thing (I just assumed that this was being done.) -- ## List details at http://www.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://www.exim.org/eximwiki/
