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 o81ANX6H128121 for ; Wed, 1 Sep 2010 05:23:33 -0500 Received: from bombadil.infradead.org (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id D78EA179B808 for ; Wed, 1 Sep 2010 03:24:12 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org [18.85.46.34]) by cuda.sgi.com with ESMTP id xGqL4i1oz4IxLmpZ for ; Wed, 01 Sep 2010 03:24:12 -0700 (PDT) Date: Wed, 1 Sep 2010 06:24:12 -0400 From: Christoph Hellwig Subject: Re: 4K drives, sectsz=512, bsize=4096 Message-ID: <20100901102412.GF31648@infradead.org> References: <201008300956.21264@zmi.at> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <201008300956.21264@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: Michael Monnerie Cc: xfs@oss.sgi.com On Mon, Aug 30, 2010 at 09:56:16AM +0200, Michael Monnerie wrote: > I have 2x 2TB 4K sector drives, joined with LVM to RAID-0. On top of > that, I created an XFS, but that has sectsz=512. > > Will there be any real difference if I re-format with sectsz=4096? > AFAIK, XFS will do I/O based on block size, so the sector size doesn't > do any harm. Is that correct? As nathan mentioned XFS issues log I/O based on the sector size, and we do allow direct I/O down to the sector size. That's two reasons why or why you don't want a 4096 byte sector size. Depending on the rmv implementation of the drive log I/O might be really slow if you set the 512 byte sector size. On the other hand there's lots of applications that have the 512 byte alignment for direct I/O hardcoded, which will break if you have a larger sector size. That's one of the fun things 4k sector size disks will bring up, especially the real 4k SAS disks that do not accept any I/O smaller than that. > A question for LVM: Is there anything I need to tell to LVM to let it > know that those are 4K sector drives and I/O should be aligned to that? > Drives are reported as 512b sectors, but really are 4K. There seems to > be no way to instruct the kernel to see those drives as 4K drives. If you have a recent enough LVM all metdata is aligned on 1MB boundaries which will do just fine. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs