From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from noc.netops.me ([50.22.23.10]:42027 "EHLO noc.netops.me" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751303AbaDTSC7 (ORCPT ); Sun, 20 Apr 2014 14:02:59 -0400 Received: from [174.77.42.16] (port=59950) by noc.netops.me with esmtpsa (TLSv1:DHE-RSA-AES128-SHA:128) (Exim 4.82) (envelope-from ) id 1WbvWA-0007j1-O7 for linux-btrfs@vger.kernel.org; Sun, 20 Apr 2014 12:27:02 -0500 Message-ID: <53540367.4050707@aeb.io> Date: Sun, 20 Apr 2014 10:27:03 -0700 From: Adam Brenner MIME-Version: 1.0 To: linux-btrfs@vger.kernel.org Subject: Slow Write Performance w/ No Cache Enabled and Different Size Drives Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: Howdy, I recently setup a new BTRFS filesystem based on BTRFS version 3.12 on Linux kernel 3.13-1 running Debian Jessie. The BTRFS volume spans 3x 4TB disks, two of which are using the entire raw block device, and one of them is using a partition (OS disks). The setup is like so: root@gra-dfs:/data/tmp# btrfs filesystem show Label: none uuid: 63d51c9b-f851-404f-b0f2-bf84d07df163 Total devices 3 FS bytes used 3.03TiB devid 1 size 3.61TiB used 1.01TiB path /dev/sda3 devid 2 size 3.64TiB used 1.04TiB path /dev/sdb devid 3 size 3.64TiB used 1.04TiB path /dev/sdc Btrfs v3.12 root@gra-dfs:/data/tmp# btrfs filesystem df /data Data, single: total=3.07TiB, used=3.03TiB System, RAID1: total=8.00MiB, used=352.00KiB System, single: total=4.00MiB, used=0.00 Metadata, RAID1: total=5.00GiB, used=3.60GiB Metadata, single: total=8.00MiB, used=0.00 root@gra-dfs:/data/tmp# root@gra-dfs:/home# mount | grep /data /dev/sda3 on /data type btrfs (rw,noatime,space_cache) root@gra-dfs:/home# The setup is supposed to be "RAID-0 like" but with different size drives within the volume, I created the BTRFS filesystem using the following command based on the WiKi[1] mkfs.btrfs -d single /dev/sda3 /dev/sdb /dev/sdc -f Once setup, I transferred roughly 3.1TB of data and noticed the write speed was limited to 200MB/s. This is the same write speed that I would see across a single device. I used dd with oflag=direct and a block size of 1M and a count of 1024 from /dev/zero. Both showed the same speeds. So my question is, should I have setup the BTRFS filesystem with -d raid0? Would this have worked with multiple devices with different sizes? [1]: https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices -- Adam Brenner