From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f175.google.com ([209.85.223.175]:36375 "EHLO mail-io0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750949AbcAZGOi (ORCPT ); Tue, 26 Jan 2016 01:14:38 -0500 Received: by mail-io0-f175.google.com with SMTP id g73so179698969ioe.3 for ; Mon, 25 Jan 2016 22:14:38 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <56A230C3.3080100@netcologne.de> <56A6082C.3030007@netcologne.de> Date: Mon, 25 Jan 2016 23:14:37 -0700 Message-ID: Subject: Re: btrfs-progs 4.4 re-balance of RAID6 is very slow / limited to one cpu core? From: Chris Murphy To: Christian Rohmann Cc: linux-btrfs Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: 1495MiB used raid6 in a VM using 4x qcow2 files on an SSD. Host is using kernel 4.4.0 Guest is using kernel 4.5.0rc0.git9.1.fc24 (this is a Fedora Rawhide debug kernel so it'll be a bit slower), btrfs-progs 4.3.1 Not degraded, balance takes 11 seconds, that's ~136MiB/s iotop isn't consistent, max is ~300MiB/s write. Reboot with 1 device missing and a new empty qcow2 in its place, mount degraded and 'btrfs replace' takes 13 seconds according to 'btrfs replace status'. I don't know that this is very useful information though. Christian, what are you getting for 'iotop -d3 -o' or 'iostat -d3'. Is it consistent or is it fluctuating all over the place? What sort of eyeball avg/min/max are you getting? Chris Murphy