Date: Tue, 17 Mar 2015 07:30:24 +0100 From: Dirk E <cipher_nl@hotmail.com> To: Dmitry Morozovsky <marck@rinet.ru>, Steven Hartland <killing@multiplay.co.uk> Cc: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org> Subject: RE: ZFS doing background writes? Message-ID: <DUB131-W2A91120F53BDE3E17E23997030@phx.gbl> In-Reply-To: <alpine.BSF.2.00.1503170451150.82898@woozle.rinet.ru> References: <DUB131-W446C7C68BD022D901F040697020@phx.gbl>, <55076B84.0@multiplay.co.uk>, <alpine.BSF.2.00.1503170451150.82898@woozle.rinet.ru>
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> On Mon=2C 16 Mar 2015=2C Steven Hartland wrote:=0A= >=0A= >> yes exactly that its defined by vfs.zfs.txg.timeout.=0A= >=0A= > Well=2C but what data (modulo atimes=2C which I presume OP had turned off= before)=0A= > are written?=0A= =0A= I indeed have atime=3Doff for the whole pool. But even with atime enabled= =2C this behaviour should not happen=2C since no files are being accessed. = Surely not in single user mode=3B the only processes outside of the kernel = were '/bin/sh' and 'top'. Or zpool iostat when i ran it.=0A= =0A= I left the machine on and after a bunch of hours it is still doing periodic= al writes. The total ARC usage remains small: 5300K and changes slightly ov= er time - again with no host writes.=0A= =0A= Even unmounting all ZFS filesystems will NOT cause this behaviour to go awa= y. It seems to originate from the ZFS kernel itself=2C doing some autonomou= s maintenance on the background=2C or other feature.'=0A= =0A= Using top to sort processes with the longest CPU TIME=2C i can see:=0A= =0A= idle: 27.9H=0A= kernel: 6:48=0A= intr: 4:34=0A= zfskern: 0:33=0A= geom: 0:29=0A= syncer: 0:16=0A= rand_harv 0:11=0A= cam: 0:09=0A= pf purge: 0:08=0A= powerd: 0:03=0A= =0A= This machine has done very little than boot and import the pool. As can be = seen=2C the kernel and ZFS are pretty active in terms of CPU power.=0A= =0A= Anyone have a clue?=0A= =
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