From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id o6KEAVl8024108 for ; Tue, 20 Jul 2010 09:10:32 -0500 Received: from firestarter.dermichi.com (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id C12A61E2DCBD for ; Tue, 20 Jul 2010 07:13:31 -0700 (PDT) Received: from firestarter.dermichi.com (firestarter.dermichi.com [78.41.115.230]) by cuda.sgi.com with ESMTP id RD5ZPlXmCMSHBOMA for ; Tue, 20 Jul 2010 07:13:31 -0700 (PDT) Received: from cl-840.mbx-01.si.sixxs.net ([2001:15c0:65ff:347::2]) by firestarter.dermichi.com with esmtpsa (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from ) id 1ObDZa-0005GV-I1 for xfs@oss.sgi.com; Tue, 20 Jul 2010 16:13:30 +0200 Message-ID: <4C45AF09.5090901@dermichi.com> Date: Tue, 20 Jul 2010 16:13:29 +0200 From: Michael Weissenbacher MIME-Version: 1.0 Subject: Re: Calculating swidth On A RAID6 Volume References: <3C5E029826A0704DB5998577FCFF46F0094DA1AD69@dagobah> <201007201522.39455@zmi.at> In-Reply-To: <201007201522.39455@zmi.at> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: xfs@oss.sgi.com Michael, >> If that is the case, then here is what I would expect my values to >> be: sunit = 512 >> swidth = 4608 > > I think sunit should be as big as the RAID controllers stripe size, as > it describes the smallest I/O XFS should do. So sunit=512 would make it > possible that XFS writes a single sector, while the RAID controller > needs to read/write 256KB with your stripe size, resulting in > performance degradation. But I'm no XFS dev, so maybe wait for a > clearing from someone who has deeper XFS knowledge than me. > > sunit=262144 > swidth=9 > > Would be my suggestion for your setup. > IIRC sunit and swidth are both specified in units of 512 bytes (don't ask me why) so a sunit value of 512 would mean 256KB stripe size which is correct :-) If i am right, the FAQ should be corrected (hopefully some dev can confirm/deny it) cheers, Michael _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs