From owner-freebsd-fs@FreeBSD.ORG Tue Jun 14 15:12:08 2011 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4C119106564A for ; Tue, 14 Jun 2011 15:12:08 +0000 (UTC) (envelope-from pvz@itassistans.se) Received: from zcs1.itassistans.net (zcs1.itassistans.net [212.112.191.37]) by mx1.freebsd.org (Postfix) with ESMTP id 023EF8FC14 for ; Tue, 14 Jun 2011 15:12:07 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by zcs1.itassistans.net (Postfix) with ESMTP id A607EC025F; Tue, 14 Jun 2011 17:12:06 +0200 (CEST) X-Virus-Scanned: amavisd-new at zcs1.itassistans.net Received: from zcs1.itassistans.net ([127.0.0.1]) by localhost (zcs1.itassistans.net [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 3vbSitlNYlbs; Tue, 14 Jun 2011 17:12:06 +0200 (CEST) Received: from [192.168.1.239] (c213-89-160-61.bredband.comhem.se [213.89.160.61]) by zcs1.itassistans.net (Postfix) with ESMTPSA id 0EBD2C01C5; Tue, 14 Jun 2011 17:12:06 +0200 (CEST) Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii From: Per von Zweigbergk In-Reply-To: <20110614150613.GB27199@DataIX.net> Date: Tue, 14 Jun 2011 17:12:05 +0200 Content-Transfer-Encoding: quoted-printable Message-Id: <61335943-0172-4483-A221-5C77CD8BAEFB@itassistans.se> References: <9544F7B9-E286-4266-86E3-B4D1A667CBBD@itassistans.se> <20110614150613.GB27199@DataIX.net> To: jhell X-Mailer: Apple Mail (2.1084) Cc: freebsd-fs@freebsd.org Subject: Re: Disk usage and ZFS deduplication X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 14 Jun 2011 15:12:08 -0000 14 jun 2011 kl. 17.06 skrev jhell: >=20 >=20 >=20 > On Tue, Jun 14, 2011 at 09:19:32AM +0200, Per von Zweigbergk wrote: >> I've been following the "Impossible compression ratio on ZFS" thread = with some interest, and it made me ask myself this: >>=20 >> Let us say we have a hypothetical zfs filesystem with the equally = hypothetical files A and B. The filesystem has deduplication enabled. = Both files have an apparent file size of 100 MB, but 50 MB of that data = is common between the two files and thus can be deduplicated. This would = mean that total disk usage would be 150 MB. >>=20 >> If you use "du" to determine disk size for a deduplication, what = would be the result? Which file would the common data be accounted to? = Or would it be accounted to both files somehow, in part or in full? >=20 > Logical answer would be that both files should be showing thier > resulting size regardless of how ZFS processes them. Being deduped = does > not mean representing files to the user any different. That would be the file size, yes, as opposed to the disk usage.=