From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: Re: curious writes on mounted, not used btrfs filesystem Date: Sun, 22 May 2011 11:52:37 +0200 Message-ID: <4DD8DCE5.6070703@wpkg.org> References: <4DD7B6ED.5040403@wpkg.org> <20110522093352.GA22491@yahoo.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Cc: linux-btrfs To: Stephane Chazelas Return-path: In-Reply-To: <20110522093352.GA22491@yahoo.fr> List-ID: On 22.05.2011 11:34, Stephane Chazelas wrote: > 2011-05-21 14:58:21 +0200, Tomasz Chmielewski: >> I have a btrfs filesystem (2.6.39) which is mounted, but otherwise, not used: >> >> # lsof -n|grep /mnt/btrfs > > processes with open fds are one thing. You could also have loop > devices setup on it for instance. I know. It's _not_ used by anything. >> # >> >> >> I noticed that whenever I do "sync", btrfs will write for around 6.5s and write 13 MB (see below). > [...] > > You could try and play with /proc/sys/vm/block_dump to see what > is being written (remember to disable logging of kernel messages > by syslog). It doesn't give me any hints, really. Can you try running these commands yourself: iostat -k 1 And in a second terminal: while true; do sync ; done To see if your btrfs makes writes on sync each time? -- Tomasz Chmielewski http://wpkg.org