From: mhaverkamp@kcp.com Subject: Re: OT: RAID perf doldrums: advice/recommendations? Date: Mon, 31 Oct 2005 09:12:27 -0600 Message-ID: References: <20051028222238.92185.qmail@web51914.mail.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Return-path: Received: from sc8-sf-mx2-b.sourceforge.net ([10.3.1.92] helo=mail.sourceforge.net) by sc8-sf-list2.sourceforge.net with esmtp (Exim 4.30) id 1EWbL7-0000MZ-31 for nfs@lists.sourceforge.net; Mon, 31 Oct 2005 07:12:49 -0800 Received: from mailhost2.os.kcp.com ([198.124.201.32]) by mail.sourceforge.net with esmtp (Exim 4.44) id 1EWbKz-0001ta-Te for nfs@lists.sourceforge.net; Mon, 31 Oct 2005 07:12:48 -0800 In-Reply-To: <20051028222238.92185.qmail@web51914.mail.yahoo.com> To: nfs@lists.sourceforge.net Sender: nfs-admin@lists.sourceforge.net Errors-To: nfs-admin@lists.sourceforge.net List-Unsubscribe: , List-Id: Discussion of NFS under Linux development, interoperability, and testing. List-Post: List-Help: List-Subscribe: , List-Archive: nfs-admin@lists.sourceforge.net wrote on 10/28/2005 05:22:38 PM: > > > If you stay with RAID5, get something with a battery backed write cache. > > That will make a huge difference in RAID5 performance. > > Really? I was under the impression that this was just a safety precaution or > similar... it is called a "backup" after all. :) How exactly does it > increase performance? Without one, writes must be flushed to disk before the RAID controller can report them as complete. This includes even trivial things like updating file access times. With one, writes only need to get into the controller's write cache before they are reported as complete. This allows the controller to schedule the actual write to disk at an optimal time. A good way to show this is to untar a tar file full of small files (e.g. kernel source). On RAID5 without write cache, this takes at least 10 times longer than even a single ATA disk. > > (And, yes, I have seen this mentioned in many places, so this would be a > criteria for our next purchase. :) ) > > > > > __________________________________ > Yahoo! Mail - PC Magazine Editors' Choice 2005 > http://mail.yahoo.com > > > ------------------------------------------------------- > This SF.Net email is sponsored by the JBoss Inc. > Get Certified Today * Register for a JBoss Training Course > Free Certification Exam for All Training Attendees Through End of 2005 > Visit http://www.jboss.com/services/certification for more information > _______________________________________________ > NFS maillist - NFS@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/nfs ------------------------------------------------------- This SF.Net email is sponsored by the JBoss Inc. Get Certified Today * Register for a JBoss Training Course Free Certification Exam for All Training Attendees Through End of 2005 Visit http://www.jboss.com/services/certification for more information _______________________________________________ NFS maillist - NFS@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/nfs