From owner-freebsd-current@FreeBSD.ORG Fri Nov 15 09:24:09 2013 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id E16E3E8 for ; Fri, 15 Nov 2013 09:24:09 +0000 (UTC) Received: from nm14-vm9.bullet.mail.ir2.yahoo.com (nm14-vm9.bullet.mail.ir2.yahoo.com [212.82.96.197]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id BD97D2A58 for ; Fri, 15 Nov 2013 09:24:08 +0000 (UTC) Received: from [212.82.98.56] by nm14.bullet.mail.ir2.yahoo.com with NNFMP; 15 Nov 2013 09:24:01 -0000 Received: from [46.228.39.97] by tm9.bullet.mail.ir2.yahoo.com with NNFMP; 15 Nov 2013 09:24:01 -0000 Received: from [127.0.0.1] by smtp134.mail.ir2.yahoo.com with NNFMP; 15 Nov 2013 09:24:01 -0000 X-Yahoo-Newman-Id: 455592.43865.bm@smtp134.mail.ir2.yahoo.com X-Yahoo-Newman-Property: ymail-3 X-YMail-OSG: vvlC8r4VM1mCfRWsvkZJWkydyqSonDsCVG6WamkDu9zhWeY VWmuToSlirQ0I9N1uxMnoHEaEEgAUdH7oahzQmDHwAAHy9FEktKQjJOuWHvk f6bvB_kpG5uBJvtCB7ppDN1Ah9PmLPx2ylaquK2hZzcHTzUDL1DNRJVOeNqa DlkXxBUX4iH.K2pXhWMPm41BV9vU5Bz6NlGHqYdDsiSgMgR2bU3X7GBuu4Dq De_AiZjC5CGMgDFEemBQsDJQ9hNnFppwEXIutuTQkmsgFOO5uCM4XuKhztUn yC011M1QVSMOsxfuGzQN0K03AlgEO8BfIXXW4yf8I_75iHJ8MjUXg3DceDdd rZYxLbIfIMJOeedYUk28bQ3FhMaFbazMz7ui9hzO6uVKtOR0oaLMeU9lw2Md Kiyzj9a92.c0iou3ZChIWiJUpA9_CESnP3Fqc.TpvRntmeLZP6P_mzckNOH8 4k25O_2qMAlvUScz1GokhtFyHeECQWUZUIO4wGNUYfthzxaQ.r7RBoFZNg76 dHpFY7JkFzC.TpU04LeysGGespxFyAg-- X-Yahoo-SMTP: iDf2N9.swBDAhYEh7VHfpgq0lnq. X-Rocket-Received: from [192.168.119.11] (se@84.154.100.25 with ) by smtp134.mail.ir2.yahoo.com with SMTP; 15 Nov 2013 09:24:01 +0000 UTC Message-ID: <5285E827.1090501@freebsd.org> Date: Fri, 15 Nov 2013 10:23:51 +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-current@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-current@freebsd.org X-Mailman-Version: 2.1.16 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 15 Nov 2013 09:24:09 -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