On Thu, Jun 3, 2010 at 1:31 PM, Greg Smith <greg@xxxxxxxxxxxxxxx> wrote: > Scott Marlowe wrote: >> >> I think it's a case of the quickest, simplest answer to semi-new tech. >> Not sure what to do with barriers? Just flush the whole cache. >> > > Well, that really is the only useful thing you can do with regular SATA > drives; the ATA command set isn't any finer grained than that in a way > that's useful for this context. And it's also quite reasonable for a RAID > controller to respond to that "flush the whole cache" call by flushing its > cache. So it's not just the simplest first answer, I believe it's the only > answer until a better ATA command set becomes available. > > I think this can only be resolved usefully for all of us at the RAID > firmware level. If the controller had some logic that said "it's OK to not > flush the cache when that call comes in if my battery is working fine", That's what already happens for fsync on a BBU controller, so I don't think the code to do so would be something fancy and new, just a simple change of logic on which code path to take. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
