Date: Fri, 10 Jan 2014 17:29:21 +0400 (MSK) From: Dmitry Morozovsky <marck@rinet.ru> To: Steven Hartland <killing@multiplay.co.uk> Cc: 'freebsd-fs' <freebsd-fs@freebsd.org> Subject: Re: What does ZFS write when nothing should write there? Message-ID: <alpine.BSF.2.00.1401101728030.24613@woozle.rinet.ru> In-Reply-To: <29BFE2939CF14317A149D6C2D68D9A8E@multiplay.co.uk> References: <52CFA0B6.7090109@fsn.hu> <alpine.BSF.2.00.1401101707430.24613@woozle.rinet.ru> <52CFF18F.5040809@fsn.hu> <29BFE2939CF14317A149D6C2D68D9A8E@multiplay.co.uk>
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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 <pool> 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? -- Sincerely, D.Marck [DM5020, MCK-RIPE, DM3-RIPN] [ FreeBSD committer: marck@FreeBSD.org ] ------------------------------------------------------------------------ *** Dmitry Morozovsky --- D.Marck --- Wild Woozle --- marck@rinet.ru *** ------------------------------------------------------------------------
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