From owner-freebsd-fs@FreeBSD.ORG Fri Jan 10 13:28:33 2014 Return-Path: Delivered-To: freebsd-fs@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 E41B2AF1 for ; Fri, 10 Jan 2014 13:28:33 +0000 (UTC) Received: from people.fsn.hu (people.fsn.hu [195.228.252.137]) (using TLSv1 with cipher ADH-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 8FA021C95 for ; Fri, 10 Jan 2014 13:28:33 +0000 (UTC) Received: by people.fsn.hu (Postfix, from userid 1001) id BD62012B003E; Fri, 10 Jan 2014 14:28:30 +0100 (CET) X-Bogosity: Ham, tests=bogofilter, spamicity=0.044161, version=1.2.3 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MF-ACE0E1EA [pR: 14.0615] X-CRM114-CacheID: sfid-20140110_14282_E3A8EEC4 X-CRM114-Status: Good ( pR: 14.0615 ) X-DSPAM-Result: Whitelisted X-DSPAM-Processed: Fri Jan 10 14:28:30 2014 X-DSPAM-Confidence: 0.9951 X-DSPAM-Probability: 0.0000 X-DSPAM-Signature: 52cff57e660512995237406 X-DSPAM-Factors: 27, From*Attila Nagy , 0.00010, wrote+>, 0.00189, >+>>, 0.00255, that+>, 0.00292, On+Fri, 0.00301, >>+On, 0.00309, >+>, 0.00323, >+>, 0.00323, From*Attila, 0.00438, zfs, 0.00438, wrote+>>>, 0.00438, wrote+>>>, 0.00438, Subject*ZFS, 0.00477, shell, 0.00477, wrote, 0.00520, wrote, 0.00520, writes, 0.00583, >>>+>>, 0.00583, References*fsn.hu>, 0.00583, References*fsn.hu>, 0.00583, writes+>, 0.00655, Nagy+wrote, 0.00655, each+time, 0.00748, >>>>+>>>>, 0.00748, Received*online.co.hu+[195.228.243.99]), 0.00872, Received*[195.228.243.99]), 0.00872, X-Spambayes-Classification: ham; 0.00 Received: from japan.t-online.private (japan.t-online.co.hu [195.228.243.99]) by people.fsn.hu (Postfix) with ESMTPSA id AD38C12B0032; Fri, 10 Jan 2014 14:28:29 +0100 (CET) Message-ID: <52CFF57D.4060804@fsn.hu> Date: Fri, 10 Jan 2014 14:28:29 +0100 From: Attila Nagy MIME-Version: 1.0 To: Steven Hartland , Dmitry Morozovsky Subject: Re: What does ZFS write when nothing should write there? References: <52CFA0B6.7090109@fsn.hu> <52CFF18F.5040809@fsn.hu> <29BFE2939CF14317A149D6C2D68D9A8E@multiplay.co.uk> In-Reply-To: <29BFE2939CF14317A149D6C2D68D9A8E@multiplay.co.uk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: 'freebsd-fs' X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.17 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 10 Jan 2014 13:28:34 -0000 On 01/10/14 14:24, Steven Hartland wrote: > ----- Original Message ----- From: "Attila Nagy" > >> On 01/10/14 14:08, Dmitry Morozovsky wrote: >>> On Fri, 10 Jan 2014, Attila Nagy wrote: >>> >>>> I've created 6 zpools, each of them with zpool create -m /data/A >>>> dataA mirror >>>> daX daY. >>>> The machine has nothing running except sshd and my shell. >>>> >>>> Yet, I see this in gstat: >>> [snip] >>> >>>> 0 88 0 0 0.0 82 573 4.1 9.0 da5 >>>> 0 89 0 0 0.0 83 573 4.8 9.8 da6 >>>> 0 87 0 0 0.0 81 573 2.6 5.7 da9 >>>> 0 89 0 0 0.0 84 573 3.0 6.7 da10 >>> Did you turn off atime? >>> >> No, but how does it matter? >> The process list is the following: init, getty, sshd, csh and the >> pool is completely empty. > > With atime on each time you access a file it will update its "atime" > hence causing writes. > > We use atime=off at the pool level on all machines to avoid that > zfs set atime=off I owe you a beer if you can explain why this matters on an empty file system on a machine, which has four processes running: init, getty, sshd and csh. :)