Odd rebalancing behavior

I have an external 4-disk enclosure, connected through USB 2.0 (my laptop does not have a USB 3.0 connector, and the eSATA connector somehow does not work); it initially had a 2-disk btrfs soft-RAID1 file system (both data and metadata are RAID1). I recently added two more disks and did a rebalance. To my surprise it went past the point where all four disks have the same amount of disk usage, and went all the way to the original disks being empty, and the new disks having all the data! Label: 'media.store' uuid: 4cfd3551-aa85-4399-b872-9238ddb14c97 Total devices 4 FS bytes used 1.22TB devid 3 size 1.82TB used 1.24TB path /dev/sdb devid 4 size 1.82TB used 1.24TB path /dev/sdc devid 2 size 1.82TB used 8.00MB path /dev/sde devid 1 size 1.82TB used 12.00MB path /dev/sdd Is this to be expected? Would another rebalance fix it, or should I force-stop it by shutting down when the disk usage is roughly balanced? This is on Fedora 15 pre-release, x86_64, fully updated, kernel 2.6.38.2-9 and btrfs-progs 0.19-13 Thanks, -- Michel Alexandre Salim GPG key ID: 78884778 () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments