From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f41.google.com ([74.125.83.41]:44337 "EHLO mail-ee0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753990Ab3AaJpX (ORCPT ); Thu, 31 Jan 2013 04:45:23 -0500 Received: by mail-ee0-f41.google.com with SMTP id c13so1318806eek.14 for ; Thu, 31 Jan 2013 01:45:21 -0800 (PST) Message-ID: <510A3D1D.4010501@statystyka.net> Date: Thu, 31 Jan 2013 10:45:01 +0100 From: Adam Ryczkowski MIME-Version: 1.0 To: andrew.j.wade@gmail.com, linux-btrfs@vger.kernel.org Subject: Re: Poor performance of btrfs. Suspected unidentified btrfs housekeeping process which writes a lot References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2013-01-31 04:33, Andrew Wade wrote: > Hi Adam, > > Is btrfs mounted relatime? I'm wondering if you're seeing metadata > writes from atime updates. I've got my filesystem mounted noatime to > avoid breaking metadata sharing between subvolumes. > > Apologies for the broken threading - I'm not subscribed to the list. > > regards, > Andrew Thank you, thank you!!! Hurray!! That was the problem!! I'm so happy you've helped me out!!! After mounting the system with noatime the problem disappeared, like in magic. All the writes must have came from the dealyed metadata copy process. Once all the metadata copy-update was done, file system speed was back to normal, but once the new day broke out, all the copying business needed to done again... This in 100% describes all the odd behavior. In particular apparently the problem had nothing to do with my complex block device setup, nor with bedup, nor with unison. Thank you again, Andrew! P.S. Maybe it is not be decided by me, but this small message about performance (not even labeled as warning) in https://btrfs.wiki.kernel.org/index.php/Mount_options IMHO should have been made more conspicuous, maybe put somewhere when the snapshot mechanism is described or in FAQ. I'll try to fix it. -- Adam Ryczkowski +48505919892 Skype:sisteczko