From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Roland" Subject: Re: multiple device usage Date: Sat, 27 Dec 2008 15:12:01 +0100 Message-ID: <000c01c9682d$16b30da0$6602a8c0@bui.materna.com> References: <556243856@web.de> <49559672.7060204@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Cc: To: "Yan Zheng" Return-path: List-ID: >> i have some difficulty in understanding multi-device handling in depth. >> >> as >> http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devices >> tells, >> >> btrfs can span over multiple devices at the same time. (great feature, >> btw !) >> >> ok then: >> >> mkfs.btrfs -m single -d single /dev/sdb /dev/sdc - creates a btrfs >> spanning >> over /dev/sdb and sdc >> >> mount /dev/sdb /btrfs - mounts it >> >> btrfs-vol -b /btrfs - does a rebalancing of all data and metadata >> >> btrfs-vol -r /dev/sdc - removes one of the volumes and redistributes any >> extends in use on sdc to sdb (killer feature!!!) >> >> but what if i want to remove /dev/sdb ? (as that one is in use for the >> mount) >> > > Devices in btrfs are equal, so you can do this. The only glitch is > /proc/mounts and mount(8) get confused. so i can do btrfs-vol -r /dev/sdb while it`s being mounted, pull the disk , replace it with a bigger one, rescan-scsi-bus, mkfs.btrfs the new disk and then re-add - all while mount telling me, that /dev/sdb is still in use !?