From owner-freebsd-fs@FreeBSD.ORG Fri Nov 15 08:59:45 2013 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 9198FBC0 for ; Fri, 15 Nov 2013 08:59:45 +0000 (UTC) Received: from nm19-vm3.bullet.mail.ir2.yahoo.com (nm19-vm3.bullet.mail.ir2.yahoo.com [212.82.96.236]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id CC21528CF for ; Fri, 15 Nov 2013 08:59:44 +0000 (UTC) Received: from [212.82.98.63] by nm19.bullet.mail.ir2.yahoo.com with NNFMP; 15 Nov 2013 08:53:27 -0000 Received: from [46.228.39.98] by tm16.bullet.mail.ir2.yahoo.com with NNFMP; 15 Nov 2013 08:53:27 -0000 Received: from [127.0.0.1] by smtp135.mail.ir2.yahoo.com with NNFMP; 15 Nov 2013 08:53:27 -0000 X-Yahoo-Newman-Id: 472508.46461.bm@smtp135.mail.ir2.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: 9tkUl2QVM1lWXGJ.oUZzij9uPRxvIdZJUnLdAm8vQUO2ivT 7l_9grkEq6nri5vOaTE3TRtbvq7LM266iPzTa6.5kj0ascLzTc3yxqB2izJv y3mwCyUOwPKpU43.L6YPY0GeHz8bxxQtrcGdeq5ZNOefudJU5.wlpFToybS9 z2V3jGpl52KkaB_5eiquA44Z0O2Qsxgf8BqVKx7HVHQOXDUAZP9bcCG2dlsX EC0__8Ro.P0.e1DLFPC58mk4Uq2tZt_Zk0e7Weng8r4HWd2oXqjM_V0kBEgl HL7AcIea3T7tlEftcNIk3ndCJ18fSn3KzWuOZ8jtFEJZ9lN1RpzlVmASS6Ae 3M37LCYsUsBadL1QEeVaE3Hb3zBLGPgyzVrUG0HYE5bO9kugkb3lmP.nSHD6 6M69ul.Ese.Glk5ohmwrB.IeRCrkr6oyG7z1UHlCAb.Ty_wJFUKKCh9XIKA2 omvANpVZp5nmsi8TXR3NVZXfulZYIEAFSIqxw.cQT.Wq_ZaVKTcLdv9.SPhA EejNsjb8C8bJAPP8u15QXaZkzZWbAmw-- X-Yahoo-SMTP: iDf2N9.swBDAhYEh7VHfpgq0lnq. X-Rocket-Received: from [192.168.119.11] (se@84.154.100.25 with ) by smtp135.mail.ir2.yahoo.com with SMTP; 15 Nov 2013 08:53:27 +0000 UTC Message-ID: <5285E0FD.8040205@freebsd.org> Date: Fri, 15 Nov 2013 09:53:17 +0100 From: Stefan Esser User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: freebsd-fs@freebsd.org Subject: Re: Defaults in 10.0 ZFS through bsdinstall References: <20131114173423.GA21761@blazingdot.com> <59A9B68B-4134-4217-83F3-B99759174EFE@fisglobal.com> <5285148E.6020903@allanjude.com> <3D3332FA-0ABF-4573-8E65-4E7FBB37100B@fisglobal.com> <1384462198.13183.47596065.6F8E7BCD@webmail.messagingengine.com> <55232624-3B76-4781-91E0-0C2A6260144D@fisglobal.com> In-Reply-To: <55232624-3B76-4781-91E0-0C2A6260144D@fisglobal.com> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.16 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Nov 2013 08:59:45 -0000 Am 14.11.2013 22:02, schrieb Teske, Devin: > On Nov 14, 2013, at 12:49 PM, Mark Felder wrote: >> We don't even do installs on UFS with atime disabled by default in fstab >> so why should we so suddenly change course for ZFS? >> > > You've made a good point. There is major difference between UFS and ZFS: UFS allows in-place updates of i-node fields (like atime), while ZFS uses COW for all data, file contents and meta-data like the i-nodes. With atime ON on UFS you'll see a small number of writes on file-systems that are only read - we are used to accept that. On ZFS every update of atime causes a write of the meta-data to a free location on disk, then updates of all data structures that reference that meta-data up to the root of the tree (the uberblock). An update of a few bytes turns out to write tens of KB for each atime update (within the TXG sync interval, which defaults to 5 seconds on FreeBSD). If you create snapshots, then each snapshot will contain a copy of the metadata that was valid at the time of the snapshot (well, that's not so different from the situation with UFS snapshots, just that the data structures are much more complex and larger in the ZFS case). Due to the ease and speed of snapshot creation with ZFS there probably are a magnitude or more snapshots on a typical ZFS system than on one using UFS (I currently have a few hundred and have turned off periodic snapshot generation on many unimportant file-systems, already). I really hope that we get relatime (with minor variations that were discussed a few months ago) and that we make it the default in some future release ... Regards, STefan