Date: Fri, 20 Mar 2015 15:53:33 +0100 From: "Ronald Klop" <ronald-lists@klop.ws> To: freebsd-fs@freebsd.org Subject: Re: ZFS doing background writes? Message-ID: <op.xvswzjnykndu52@ronaldradial.radialsg.local> In-Reply-To: <DUB131-W2A91120F53BDE3E17E23997030@phx.gbl> References: <DUB131-W446C7C68BD022D901F040697020@phx.gbl> <55076B84.0@multiplay.co.uk> <alpine.BSF.2.00.1503170451150.82898@woozle.rinet.ru> <DUB131-W2A91120F53BDE3E17E23997030@phx.gbl>
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On Tue, 17 Mar 2015 07:30:24 +0100, Dirk E <cipher_nl@hotmail.com> wrote: >> On Mon, 16 Mar 2015, Steven Hartland wrote: >> >>> yes exactly that its defined by vfs.zfs.txg.timeout. >> >> Well, but what data (modulo atimes, which I presume OP had turned off >> before) >> are written? > > I indeed have atime=off for the whole pool. But even with atime enabled, > this behaviour should not happen, since no files are being accessed. > Surely not in single user mode; the only processes outside of the kernel > were '/bin/sh' and 'top'. Or zpool iostat when i ran it. > > I left the machine on and after a bunch of hours it is still doing > periodical writes. The total ARC usage remains small: 5300K and changes > slightly over time - again with no host writes. > > Even unmounting all ZFS filesystems will NOT cause this behaviour to go > away. It seems to originate from the ZFS kernel itself, doing some > autonomous maintenance on the background, or other feature.' > > Using top to sort processes with the longest CPU TIME, i can see: > > idle: 27.9H > kernel: 6:48 > intr: 4:34 > zfskern: 0:33 > geom: 0:29 > syncer: 0:16 > rand_harv 0:11 > cam: 0:09 > pf purge: 0:08 > powerd: 0:03 > > This machine has done very little than boot and import the pool. As can > be seen, the kernel and ZFS are pretty active in terms of CPU power. > > Anyone have a clue? It sounds like I have the same problem. I did not get much reply on my question: https://lists.freebsd.org/pipermail/freebsd-fs/2014-September/020004.html Regards, Ronald.
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