From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id o6R3P97v160424 for ; Mon, 26 Jul 2010 22:25:09 -0500 Received: from mail.internode.on.net (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 8F4DD12BAC2E for ; Mon, 26 Jul 2010 20:35:29 -0700 (PDT) Received: from mail.internode.on.net (bld-mail15.adl6.internode.on.net [150.101.137.100]) by cuda.sgi.com with ESMTP id hwSJEzQXXv7pTIUy for ; Mon, 26 Jul 2010 20:35:29 -0700 (PDT) Date: Tue, 27 Jul 2010 13:28:08 +1000 From: Dave Chinner Subject: Re: mkfs.xfs: cannot (re)set log sunit=0 Message-ID: <20100727032808.GM7362@dastard> References: <20100726101238.GA7725@darkside.kls.lan> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20100726101238.GA7725@darkside.kls.lan> 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: Mario 'BitKoenig' Holbe , xfs@oss.sgi.com On Mon, Jul 26, 2010 at 12:12:39PM +0200, Mario 'BitKoenig' Holbe wrote: > Hello, > > I intend to set up a XFS filesystem on a RAID0 (Linux md) with 512k > Chunk Size. Since I cannot align the log section sunit to 512k, and > since the filesystem will have not much write activity anyways (in fact, > it'll be mounted read-only most of the time), I tried not to align the > log section sunit at all via -l sunit=0, but this does not appear to > work: Of course - when you specific a value yourself, it has to be a valid value and for version 2 logs that minimum value for th lsunit is one log block. Given that: .... > log =internal log bsize=4096 blocks=2560, version=2 .... ^^^^^^^^^^ Your log block size is 4k, then: > Is this a bug or a feature? > > The minimum I was able to limit the log sunit to was -l sunit=8, i.e. 1 > block. This is the correct minimum you are allowed to specify. > Is there a difference between sunit=0 and sunit=1 in practice or > are single log entries aligned to blocks anyways? sunit=0 is an invalid configuration for a version 2 log. Filesystems without a data sunit default to a lsunit = 1 log block, so in practice version 2 logs are always aligned/padded in some way. > Btw... > Since the filesystem is mostly read-only, I was also thinking about > reducing the size of the log section. The planned filesystem will be > 5.5T or bigger, which results in 2G log section per default. I thought > about limiting it to 128M or 64M. There will be no concurrent write > activity on the fs. Together with the zero-alignment, what do you think > about that? That'll be fine - the maximum log size until a couple of years ago was 128MB, and I still do most of my benchmarking with a log that size.... Cheers, Dave. -- Dave Chinner david@fromorbit.com _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs