Date: Fri, 10 Jan 2014 14:28:29 +0100 From: Attila Nagy <bra@fsn.hu> To: Steven Hartland <killing@multiplay.co.uk>, Dmitry Morozovsky <marck@rinet.ru> Cc: 'freebsd-fs' <freebsd-fs@freebsd.org> Subject: Re: What does ZFS write when nothing should write there? Message-ID: <52CFF57D.4060804@fsn.hu> 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 01/10/14 14:24, Steven Hartland wrote: > ----- Original Message ----- From: "Attila Nagy" <bra@fsn.hu> > >> 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 <pool> 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. :)
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