From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Drebes Subject: Unable to mount loopback devices in RAID mode Date: Thu, 19 Nov 2009 20:26:04 +0100 Message-ID: <200911192026.04694.lists-receive@programmierforen.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" To: linux-btrfs@vger.kernel.org Return-path: List-ID: Hi! I recently tried to mount a filesystem in RAID1 mode using loopback devices. I followed the instructions at [1]. Here's exactly what I've done: $ dd if=/dev/zero of=raid1_0.img bs=1M count=500 $ dd if=/dev/zero of=raid1_1.img bs=1M count=500 $ mkfs.btrfs -m raid1 -d raid1 raid1_0.img raid1_1.img $ losetup /dev/loop0 raid1_0.img $ losetup /dev/loop1 raid1_1.img $ mount -t btrfs /dev/loop0 /mnt/btrfs mount: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so $ dmesg ... [ 301.429030] Btrfs loaded [ 301.439361] device fsid 7347e7099a1ddaab-c4f037e2686afdbf devid 1 transid 7 /dev/loop0 [ 301.444425] btrfs: failed to read the system array on loop0 [ 301.444480] btrfs: open_ctree failed Am I missing something? Or is the documentation outdated? The error is perfectly reproducible, no matter what RAID type I specify (raid0, raid1 or raid10). I used the latest version from the btrfs-unstable and btrfs-progs-unstable git repositories. When using real block devices, however, everything works fine. Cheers, Andi [1] http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices