On Fri, Mar 25, 2011 at 8:07 AM, Gurjeet Singh <singh.gurj...@gmail.com> wrote: > On Tue, Mar 22, 2011 at 3:53 PM, Robert Haas <robertmh...@gmail.com> wrote: >> >> On Tue, Mar 22, 2011 at 11:24 AM, Jeff Janes <jeff.ja...@gmail.com> wrote: >> > On Fri, Mar 18, 2011 at 9:19 AM, Robert Haas <robertmh...@gmail.com> >> > wrote: >> >> >> >> A related area that could use some looking at is why performance tops >> >> out at shared_buffers ~8GB and starts to fall thereafter. >> > >> > Under what circumstances does this happen? Can a simple pgbench -S >> > with a large scaling factor elicit this behavior? >> >> To be honest, I'm mostly just reporting what I've heard Greg Smith say >> on this topic. I don't have any machine with that kind of RAM. > > I can sponsor a few hours (say 10) of one High-memory on-demand Quadruple > Extra Large instance (26 EC2 Compute Units (8 virtual cores with 3.25 EC2 > Compute Units each), 1690 GB of local instance storage, 64-bit platform). > That's the largest memory AWS has.
Does AWS have machines with battery-backed write cache? I think people running servers with 192G probably have BBWC, so it may be hard to do realistic tests without also having one on the test machine. But probably a bigger problem is that (to the best of my knowledge) we don't seem to have a non-proprietary, generally implementable benchmark system or load-generator which is known to demonstrate the problem. Cheers, Jeff -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
