From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 29 Jun 2001 06:14:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 29 Jun 2001 06:14:03 -0400 Received: from lsmls01.we.mediaone.net ([24.130.1.20]:64747 "EHLO lsmls01.we.mediaone.net") by vger.kernel.org with ESMTP id ; Fri, 29 Jun 2001 06:13:54 -0400 Message-ID: <3B3C5571.3259CD32@kegel.com> Date: Fri, 29 Jun 2001 03:16:17 -0700 From: Dan Kegel X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.2.14-5.0 i686) X-Accept-Language: en MIME-Version: 1.0 To: Alan Cox CC: "linux-kernel@vger.kernel.org" Subject: Re: O_DIRECT please; Sybase 12.5 In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Alan Cox wrote: > > > the boss say "If Linux makes Sybase go through the page cache on > > reads, maybe we'll just have to switch to Solaris. That's > > a serious performance problem." > > Thats something you'd have to benchmark. It depends on a very large number > of factors including whether the database uses mmap, the average I/O size > and the like I'll probably benchmark raw vs. non-raw I/O with Sybase ASE 12.5 on our application once we've come up to speed on basic performance issues (we're database newbies). > > It supports raw partitions, which is good; that might satisfy my > > boss (although the administration will be a pain, and I'm not > > sure whether it's really supported by Dell RAID devices). > > I'd prefer O_DIRECT :-( > > We already support raw direct I/O to devices themselves so they should support > that - if not then Oracle I believe already does. Haven't seen Sybase talk about O_DIRECT. Not sure we want to pony up the Sybase license fees. (I'm still in denial about databases in general, and hope I can switch to PostgreSQL at some point.) BTW, http://eval.veritas.com/webfiles/whitepapers/sybaseedition/sybase14_performance_paper.pdf seems to show that raw beats O_DIRECT hands down on Solaris. Will that hold on Linux, or is your (forthcoming?) O_DIRECT higher performance than the one on Solaris? Thanks, Dan