Joshua D. Drake wrote: > On Sat, 2009-03-14 at 05:25 +0100, Marco Colombo wrote: >> Scott Marlowe wrote: > >> Also see: >> http://lkml.org/lkml/2008/2/26/41 >> but it seems to me that all this discussion is under the assuption that >> disks have write-back caches. >> "The alternative is to disable the disk write cache." says it all. > > If this applies to raid based cache as well then performance is going to > completely tank. For users of Linux + PostgreSQL using LVM. > > Joshua D. Drake Yet that's not the point. The point is safety. I may have a lightly loaded database, with low write rate, but still I want it to be reliable. I just want to know if disabling the caches makes it reliable or not. People on LK seem to think it does. And it seems to me they may have a point. fsync() is a flush operation on the block device, not a write barrier. LVM doesn't pass write barriers down, but that doesn't mean it doesn't perform a flush when requested to. .TM. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
