address@hidden ~]# dd if=/dev/zero of=/tmp/test0 bs=1 count=0 seek=256G
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.000171689 s, 0.0 kB/s
address@hidden ~]# dd if=/dev/zero of=/tmp/test1 bs=1 count=0 seek=256G
0+0 records in
0+0 records out
0 bytes (0 B) copied, 0.00021268 s, 0.0 kB/s
address@hidden ~]# losetup -f --show /tmp/test0
/dev/loop0
address@hidden ~]# losetup -f --show /tmp/test1
/dev/loop1
address@hidden ~]# mkfs.btrfs -mraid1 -draid1 /dev/loop0 /dev/loop1

WARNING! - Btrfs Btrfs v0.19 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

adding device /dev/loop1 id 2
fs created label btrfs-test on /dev/loop0
        nodesize 4096 leafsize 4096 sectorsize 4096 size 512.00GB
Btrfs Btrfs v0.19
address@hidden ~]# mkdir /mnt/grubtest
address@hidden ~]# losetup -d /dev/loop1
address@hidden ~]# mount -odegraded /dev/loop0 /mnt/grubtest
address@hidden ~]# grub-probe /mnt/grubtest
btrfs
address@hidden ~]# grub-probe -V
grub-probe (GRUB) 2.00
address@hidden ~]# pacman -Qs grub
local/grub-bios 2.00-1
    GNU GRand Unified Bootloader - i386 PC BIOS Modules
local/grub-common 2.00-1
    GNU GRand Unified Bootloader - Utilities and Common Files
address@hidden ~]# umount /mnt/grubtest
address@hidden ~]# losetup -d /dev/loop0
address@hidden ~]# ls -lscrath /tmp/test*
4.1M -rw-r--r-- 1 root root 256G Dec 31 10:19 /tmp/test1
5.2M -rw-r--r-- 1 root root 256G Dec 31 10:32 /tmp/test0
address@hidden ~]# rm /tmp/test[01]
address@hidden ~]# logout