On Tue, Apr 28, 2009 at 12:40 PM, Kenneth Marshall <ktm@xxxxxxxx> wrote: > On Tue, Apr 28, 2009 at 01:30:59PM -0500, Kevin Grittner wrote: >> Craig James <craig_james@xxxxxxxxxxxxxx> wrote: >> >> > After a reading various articles, I thought that "noop" was the >> > right choice when you're using a battery-backed RAID controller. >> > The RAID controller is going to cache all data and reschedule the >> > writes anyway, so the kernal schedule is irrelevant at best, and can >> > slow things down. >> >> Wouldn't that depend on the relative sizes of those caches? In a >> not-so-hypothetical example, we have machines with 120 GB OS cache, >> and 256 MB BBU RAID controller cache. We seem to benefit from >> elevator=deadline at the OS level. >> >> -Kevin >> > This was my understanding as well. If your RAID controller had a > lot of well managed cache, then the noop scheduler was a win. Less > performant RAID controllers benefit from teh deadline scheduler. I have an Areca 1680ix with 512M cache on a machine with 32Gig ram and I get slightly better performance and lower load factors from deadline than from noop, but it's not by much. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
