From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mr003msb.fastweb.it ([85.18.95.87]:53942 "EHLO mr003msb.fastweb.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750926AbdIKWOW (ORCPT ); Mon, 11 Sep 2017 18:14:22 -0400 Subject: Re: XFS and sector size on thin volumes MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Tue, 12 Sep 2017 00:14:19 +0200 From: Gionatan Danti In-Reply-To: <20170909235323.GL17782@dastard> References: <20170909231215.GK17782@dastard> <0c59ba403f83e571d695a716ccad5d0a@assyoma.it> <20170909235323.GL17782@dastard> Message-ID: <838841738c3d8ca84328075615f95475@assyoma.it> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Dave Chinner Cc: linux-xfs@vger.kernel.org, g.danti@assyoma.it > If a block device is presented with 512 sectors on 4k-only sector > drives, then that's a bug. If it's doing so with 512e drives, > then that's still a bug because it should be presenting as a > 512 byte logical, 4096 byte physical sector size device and in that > case mkfs.xfs will choose 4k sectors by default. > > IOWs, if the underlying device is correctly presented to mkfs.xfs > then it will choose the correct sector size by default. dm-thinp > does the right thing with sector sizes, but I have no idea about > ZoL. Hi Dave, it seems ZVOLs behave... interestingly... # 4K volume [root@blackhole ~]# zfs create tank/vol1 -V 300M -b 4k [root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt /dev/zvol/tank/vol1 512 4096 4096 4096 # 8K volume [root@blackhole ~]# zfs create tank/vol1 -V 300M -b 8k [root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt /dev/zvol/tank/vol1 512 8192 8192 8192 # 128K volume [root@blackhole ~]# zfs create tank/vol1 -V 300M -b 128k [root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt /dev/zvol/tank/vol1 512 131072 131072 131072 So, it seems that volume's block size does not only change the iomin/ioopt values, but pbsz also. On the other hand, ss is stuck at 512B, even if I am using a 512e (4K physical sector size) underlying disk: [root@blackhole ~]# blockdev --getss --getpbsz --getiomin --getioopt /dev/sdc 512 4096 4096 0 Creating an XFS filesystem on such a ZVOL will issue the following message: "specified blocksize 4096 is less than device physical sector size 8192 switching to logical sector size 512" In this case, should I specify block size (-b size=4k) at mkfs.xfs time, or not? Thanks. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8