From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Lutomirski Subject: How to remove a device on a RAID-1 before replacing it? Date: Tue, 29 Mar 2011 16:09:36 -0400 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: linux-btrfs Return-path: List-ID: I have a disk with a SMART failure. It still works but I assume it'll fail sooner or later. I want to remove it from my btrfs volume, replace it, and add the new one. But the obvious command doesn't work: # btrfs device delete /dev/dm-5 /mnt/foo ERROR: error removing the device '/dev/dm-5' dmesg says: btrfs: unable to go below two devices on raid1 With mdadm, I would fail the device, remove it, run degraded until I get a new device, and hot-add that device. With btrfs, I'd like some confirmation from the fs that data is balanced appropriately so I won't get data loss if I just yank the drive. And I don't even know how to tell btrfs to release the drive so I can safely remove it. (Mounting with -o degraded doesn't help. I could umount, remove the disk, then remount, but that feels like a hack.) This is 2.6.38.1 running Fedora 14's version of btrfs-progs, but btrfs-progs-unstable git does the same thing, as does btrfs-vol -r. --Andy