From owner-freebsd-fs@FreeBSD.ORG Fri Jan 10 14:18:49 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 41553986 for ; Fri, 10 Jan 2014 14:18:49 +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 DF2501FF7 for ; Fri, 10 Jan 2014 14:18:48 +0000 (UTC) Received: by people.fsn.hu (Postfix, from userid 1001) id BE93812B029F; Fri, 10 Jan 2014 15:18:45 +0100 (CET) X-Bogosity: Ham, tests=bogofilter, spamicity=0.008505, version=1.2.3 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MF-ACE0E1EA [pR: 11.0847] X-CRM114-CacheID: sfid-20140110_15184_7F41C7B2 X-CRM114-Status: Good ( pR: 11.0847 ) X-DSPAM-Result: Whitelisted X-DSPAM-Processed: Fri Jan 10 15:18:45 2014 X-DSPAM-Confidence: 0.9947 X-DSPAM-Probability: 0.0000 X-DSPAM-Signature: 52d00145893637888713381 X-DSPAM-Factors: 27, From*Attila Nagy , 0.00010, >+On, 0.00049, kernel, 0.00088, wrote+>, 0.00189, wrote+>, 0.00189, On+Fri, 0.00301, >>+>>, 0.00362, ZFS, 0.00438, From*Attila, 0.00438, zfs, 0.00438, Subject*ZFS, 0.00477, shell, 0.00477, wrote, 0.00520, wrote, 0.00520, writes, 0.00583, References*fsn.hu>, 0.00583, References*fsn.hu>, 0.00583, root, 0.00610, each+time, 0.00748, Received*online.co.hu+[195.228.243.99]), 0.00872, 14+29, 0.00872, Received*[195.228.243.99]), 0.00872, Received*online.co.hu, 0.00872, From*Attila+Nagy, 0.00872, Received*(japan.t, 0.00872, From*Nagy+ Date: Fri, 10 Jan 2014 15:18:43 +0100 From: Attila Nagy MIME-Version: 1.0 To: Dmitry Morozovsky , Steven Hartland 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: 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 14:18:49 -0000 On 01/10/14 14:29, Dmitry Morozovsky wrote: > On Fri, 10 Jan 2014, Steven Hartland 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 > BTW, it seems that ZFS updates atime of some inodes (root one?) on every kernel > update thread invocation even when completely empty -- is it correct behaviour? > Because there are no files, it must (?) be the root. But at this frequency?