Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id 4839C64FCE1 for ; Fri, 8 Aug 2008 19:30:14 -0300 (ADT) Received: from postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 90241-04 for ; Fri, 8 Aug 2008 19:30:07 -0300 (ADT) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from westnet.com (westnet.com [216.187.52.2]) by postgresql.org (Postfix) with ESMTP id EB28F64FCD6 for ; Fri, 8 Aug 2008 19:30:10 -0300 (ADT) Received: from westnet.com (localhost [127.0.0.1]) by westnet.com (8.14.0/8.14.0) with ESMTP id m78MU8UB024734; Fri, 8 Aug 2008 18:30:08 -0400 (EDT) Received: from localhost (gsmith@localhost) by westnet.com (8.14.0/8.13.2/Submit) with ESMTP id m78MU7XH024730; Fri, 8 Aug 2008 18:30:07 -0400 (EDT) X-Authentication-Warning: westnet.com: gsmith owned process doing -bs Date: Fri, 8 Aug 2008 18:30:07 -0400 (EDT) From: Greg Smith X-X-Sender: gsmith@westnet.com To: Mark Mielke cc: Andrej Ricnik-Bay , Scott Marlowe , "pgsql-performance@postgresql.org" Subject: Re: file system and raid performance In-Reply-To: <489B727B.6010800@mark.mielke.cc> Message-ID: References: <70c01d1d0808042154u7b78d988vac1e461a93b0ba10@mail.gmail.com> <70c01d1d0808050800j7196922bt2c4b43ba09a19099@mail.gmail.com> <4898E80A.3020809@paradise.net.nz> <489A3B75.6060004@paradise.net.nz> <489AC2F0.9050907@paradise.net.nz> <489ACC90.9030401@sime.com> <70c01d1d0808071236u36fe5002w833582b036d952e8@mail.gmail.com> <489B727B.6010800@mark.mielke.cc> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Virus-Scanned: Maia Mailguard 1.0.1 X-Spam-Status: No, hits=0 tagged_above=0 required=5 tests=none X-Spam-Level: X-Archive-Number: 200808/79 X-Sequence-Number: 30960 On Thu, 7 Aug 2008, Mark Mielke wrote: > Now, modern Linux distributions default to "relatime" Right, but Mark's HP test system is running Gentoo. (ducks) According to http://brainstorm.ubuntu.com/idea/2369/ relatime is the default for Fedora 8, Mandriva 2008, Pardus, and Ubuntu 8.04. Anyway, there aren't many actual files involved in this test, and I suspect the atime writes are just being cached until forced out to disk only periodically. You need to run something that accesses more files and/or regularly forces sync to disk periodically to get a more database-like situation where the atime writes degrade performance. Note how Joshua Drake's ext2 vs. ext3 comparison, which does show a large difference here, was run with the iozone's -e parameter that flushes the writes with fsync. I don't see anything like that in the DL380 G5 fio tests. -- * Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD