Date: Fri, 10 Jan 2014 16:05:51 +0100 From: "Ronald Klop" <ronald-lists@klop.ws> To: freebsd-fs@freebsd.org Subject: Re: What does ZFS write when nothing should write there? Message-ID: <op.w9g771vukndu52@ronaldradial.radialsg.local> In-Reply-To: <52D00143.9060603@fsn.hu> References: <52CFA0B6.7090109@fsn.hu> <alpine.BSF.2.00.1401101707430.24613@woozle.rinet.ru> <52CFF18F.5040809@fsn.hu> <29BFE2939CF14317A149D6C2D68D9A8E@multiplay.co.uk> <alpine.BSF.2.00.1401101728030.24613@woozle.rinet.ru> <52D00143.9060603@fsn.hu>
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On Fri, 10 Jan 2014 15:18:43 +0100, Attila Nagy <bra@fsn.hu> wrote: > 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 <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? >> > Because there are no files, it must (?) be the root. But at this > frequency? Some dtrace commands might give enlightenment. Ronald
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