From owner-freebsd-fs@FreeBSD.ORG Fri Mar 20 15:08:55 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 359D461F for ; Fri, 20 Mar 2015 15:08:55 +0000 (UTC) Received: from smarthost1.greenhost.nl (smarthost1.greenhost.nl [195.190.28.81]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id E943196A for ; Fri, 20 Mar 2015 15:08:54 +0000 (UTC) Received: from smtp.greenhost.nl ([213.108.104.138]) by smarthost1.greenhost.nl with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.72) (envelope-from ) id 1YYyIo-0001F8-AC for freebsd-fs@freebsd.org; Fri, 20 Mar 2015 15:53:39 +0100 Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes To: freebsd-fs@freebsd.org Subject: Re: ZFS doing background writes? References: <55076B84.0@multiplay.co.uk> Date: Fri, 20 Mar 2015 15:53:33 +0100 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: "Ronald Klop" Message-ID: In-Reply-To: User-Agent: Opera Mail/1.0 (Win32) X-Authenticated-As-Hash: 398f5522cb258ce43cb679602f8cfe8b62a256d1 X-Virus-Scanned: by clamav at smarthost1.samage.net X-Spam-Level: - X-Spam-Score: -1.0 X-Spam-Status: No, score=-1.0 required=5.0 tests=ALL_TRUSTED, BAYES_40 autolearn=disabled version=3.3.1 X-Scan-Signature: 788438cbfdc4dc137ce560360a3a99c7 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: Fri, 20 Mar 2015 15:08:55 -0000 On Tue, 17 Mar 2015 07:30:24 +0100, Dirk E 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.