From owner-freebsd-fs@FreeBSD.ORG Tue Mar 17 06:31:36 2015 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id F042D3D2 for ; Tue, 17 Mar 2015 06:31:36 +0000 (UTC) Received: from DUB004-OMC3S13.hotmail.com (dub004-omc3s13.hotmail.com [157.55.2.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (Client CN "*.outlook.com", Issuer "MSIT Machine Auth CA 2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 74BF087B for ; Tue, 17 Mar 2015 06:31:35 +0000 (UTC) Received: from DUB131-W2 ([157.55.2.7]) by DUB004-OMC3S13.hotmail.com over TLS secured channel with Microsoft SMTPSVC(7.5.7601.22751); Mon, 16 Mar 2015 23:30:24 -0700 X-TMN: [blAlu1yxIC5WhcJ7gpiPfh9BykkBfgX+] X-Originating-Email: [cipher_nl@hotmail.com] Message-ID: From: Dirk E To: Dmitry Morozovsky , Steven Hartland Subject: RE: ZFS doing background writes? Date: Tue, 17 Mar 2015 07:30:24 +0100 Importance: Normal In-Reply-To: References: , <55076B84.0@multiplay.co.uk>, Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginalArrivalTime: 17 Mar 2015 06:30:24.0458 (UTC) FILETIME=[D9C562A0:01D0607B] Cc: "freebsd-fs@freebsd.org" X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 17 Mar 2015 06:31:37 -0000 > 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= =