From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from relay.sgi.com (relay1.corp.sgi.com [137.38.102.111]) by oss.sgi.com (Postfix) with ESMTP id 04FEA7F55 for ; Tue, 3 Nov 2015 07:02:53 -0600 (CST) Received: from cuda.sgi.com (cuda3.sgi.com [192.48.176.15]) by relay1.corp.sgi.com (Postfix) with ESMTP id E70938F8035 for ; Tue, 3 Nov 2015 05:02:49 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by cuda.sgi.com with ESMTP id wzFuyrSAdJah751a (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Tue, 03 Nov 2015 05:02:49 -0800 (PST) Date: Tue, 3 Nov 2015 08:02:46 -0500 From: Brian Foster Subject: Re: Is it possible to change sunit of log section post-mkfs Message-ID: <20151103130246.GA24445@bfoster.bfoster> References: <5638A62D.1020802@dermichi.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <5638A62D.1020802@dermichi.com> 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 Errors-To: xfs-bounces@oss.sgi.com Sender: xfs-bounces@oss.sgi.com To: Michael Weissenbacher Cc: xfs@oss.sgi.com On Tue, Nov 03, 2015 at 01:18:53PM +0100, Michael Weissenbacher wrote: > Hi! > I have a XFS file system which lies on a 10-disk RAID-6 device that was > created with Chunk Size = 1MiB. > On mkfs.xfs time this was - as far as i know - specified with "-d > su=1m,sw=8". > > xfs_info shows the following: > meta-data=/dev/sdb1 isize=256 agcount=15, > agsize=268435200 blks > = sectsz=512 attr=2 > data = bsize=4096 blocks=3905945088, imaxpct=5 > = sunit=256 swidth=2048 blks > naming =version 2 bsize=4096 ascii-ci=0 > log =internal bsize=4096 blocks=521728, version=2 > = sectsz=512 sunit=8 blks, lazy-count=1 > realtime =none extsz=4096 blocks=0, rtextents=0 > > Interestingly, the sunit value of the log seems to be incorrect - as it > should be 256 too, like the sunit value of the data. I am pretty sure > the reason is that the log sunit cannot be 256 blks (=1024KiB) and > because of this mkfs.xfs did fall back to the default of 8 blks > (=32KiB). I found evidence of this in the following thread: > http://oss.sgi.com/archives/xfs/2012-06/msg00431.html > > What i want to achieve is to set the log sunit to the maximum possible > of 64 blks (=256KiB). > > - Is that even possible without doing mkfs.xfs (and losing all data)? > - Would it be an improvement performance-wise? > - Would changing to an external log help? > I don't believe there's any supported way to do this. Out of curiosity, I just tried an experiment to modify the superblock logsunit via xfs_db and run repair to zero the log. That seemed to work in terms of taking effect on the subsequent mount, but that's certainly not something I would suggest to do in production. Note that mkfs aligns the physical log based on the stripe unit as well, so it wouldn't really have the same effect anyways. Brian > tia, > Michael > > _______________________________________________ > xfs mailing list > xfs@oss.sgi.com > http://oss.sgi.com/mailman/listinfo/xfs _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs