How to create btrfs RAID-1 filesystem (assertion error in mkfs.btrfs)?
- by amcnabb
I tried to make a btrfs RAID-1 filesystem in "degraded mode" by following the btrfs UseCases instructions but hit a fatal assertion error. Why is this failing, and is there any workaround?
The instructions I followed are at:
https://btrfs.wiki.kernel.org/articles/u/s/e/UseCases_8bd8.html
The output of the mkfs.btrfs and btrfs filesystem show commands is:
# mkfs.btrfs -m raid1 -d raid1 /dev/sdd1 /dev/loop1
WARNING! - Btrfs Btrfs v0.19 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using
failed to read /dev/sr0
adding device /dev/loop1 id 2
mkfs.btrfs: volumes.c:802: btrfs_alloc_chunk: Assertion `!(ret)' failed.
zsh: abort (core dumped) mkfs.btrfs -m raid1 -d raid1 /dev/sdd1 /dev/loop1
# btrfs filesystem show
failed to read /dev/sr0
Label: none uuid: 773908b8-acca-4c30-85c5-6642b06de22b
Total devices 1 FS bytes used 28.00KB
devid 1 size 223.13GB used 2.04GB path /dev/sda5
Label: none uuid: 0f06f1a8-5f5f-4b92-a55c-b827bcbcc840
Total devices 2 FS bytes used 24.00KB
devid 2 size 2.00GB used 0.00 path /dev/loop1
devid 1 size 1.36TB used 20.00MB path /dev/sdd1
Btrfs Btrfs v0.19
#
EDIT:
It turns out that the filesystem isn't mountable:
# mount /dev/sdd1 /mnt/big2
mount: wrong fs type, bad option, bad superblock on /dev/sdd1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
#
So, why did the mkfs fail, and is there any workaround?
