From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx14.extmail.prod.ext.phx2.redhat.com [10.5.110.19]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id r8SKgCIS025752 for ; Sat, 28 Sep 2013 16:42:12 -0400 Received: from Ishtar.tlinx.org (ishtar.tlinx.org [173.164.175.65]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r8SKgAl7002207 for ; Sat, 28 Sep 2013 16:42:11 -0400 Received: from [192.168.4.12] (Athenae [192.168.4.12]) by Ishtar.tlinx.org (8.14.7/8.14.4/SuSE Linux 0.8) with ESMTP id r8SKg6N7002733 for ; Sat, 28 Sep 2013 13:42:09 -0700 Message-ID: <52473F1E.80704@tlinx.org> Date: Sat, 28 Sep 2013 13:42:06 -0700 From: "Linda A. Walsh" MIME-Version: 1.0 References: <521871FD.8000700@mglug.de> <5225B49B.6050904@redhat.com> In-Reply-To: <5225B49B.6050904@redhat.com> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] buffers shared between different devs? (was: howto speed-up thinpool-devices?) Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development On 9/3/2013 3:06 AM, Marian Csontos wrote: > Buffers may be more relevant metric as the I/O among snapshots is > "shared" on block device level. ---- I am not going to say this isn't true, BUT, some parts of the kernel seem to report different block numbers for files on the same device when you mount the same device (or possible subtrees of a same device) at alternate mount points via "bind". I have my "/usr/share" physically located on my "/home" partition under "/home/share". In moving files from /usr/share/ to /home/share/, the coreutils "mv" cmd, actually does a file copy -- vs. when a file is detected as being on the same device, it usually does a simple rename. If 'mv' is seeing different device id's for a file, it's *less probable*, but possible that such misinformation could exist at lower levels in the kernel (?). Do you know whether or not the kernel "knows" they are on the same device, or is it possible the buffer area of the kernel has the same bug as the upper level that is reporting different devices to "mv"?