#2028 Issue open: BTRFS Raid / Multi Disk setup is currently not supported¶
Labels: needs sponsorship, severe improvement
ChojinDSL opened issue at 2019-02-01 16:41:¶
I've noticed that ReaR doesn't correctly work with a BTRFS Multiple Disk setup.
E.g. a BTRFS Volume can consist of multiple disks in a variety of configurations, e.g. single, RAID1, RAID10, RAID5/6, etc..
It seems as if ReaR only creates a single disk BTRFS Volume during recovery. This could create problem if the backup is larger than a single disk.
Since BTRFS supports many mixed configurations, e.g. Metadata as RAID1
but Data as RAID10, accurately detecting the original layout might be
tricky.
However, at the very least it would be very nice if ReaR could detect if
a BTRFS Volume consists of multiple devices and then re-creates the
BTRFS volume with the member devices during recovery.
If you create the BTRFS volume with just a list of devices, then per default the volume will be created as a "single" volume, but with the total capacity of all member devices. Since BTRFS supports rebalancing to migrate from single to RAID1/10/5/6, it would be easy for the user to rebalance their system back to their original layout, after recovery has taken place and the system has bootet into the OS.
jsmeix commented at 2019-02-05 10:04:¶
I implemented the current Btrfs support in ReaR and
I never had a Btrfs setup on multiple disks
so that I think you are right that currently
ReaR does not support a Btrfs filesystem that is on more than one
partition.
See
"Disk layout file syntax" at
https://github.com/rear/rear/blob/master/doc/user-guide/06-layout-configuration.adoc
that reads (excerpt)
Filesystems
fs <device> <mountpoint> <filesystem type> [uuid=<uuid>] [label=<label>] [blocksize=<block size(B)>] [<reserved_blocks=<nr of reserved blocks>] [max_mounts=<nr>] [check_interval=<number of days>d] [options=<filesystem options>]
Btrfs Default SubVolumes
btrfsdefaultsubvol <device> <mountpoint> <btrfs_subvolume_ID> <btrfs_subvolume_path>
Btrfs Normal SubVolumes
btrfsnormalsubvol <device> <mountpoint> <btrfs_subvolume_ID> <btrfs_subvolume_path>
Btrfs Mounted SubVolumes
btrfsmountedsubvol <device> <subvolume_mountpoint> <mount_options> <btrfs_subvolume_path>
where all show only device but no devices.
See also
https://github.com/rear/rear/issues/2023
jsmeix commented at 2019-02-05 11:43:¶
@ChojinDSL
to get an idea how a Btrfs setup on multiple disks could look like
could you please post here the output of the command
lsblk -i -p -o NAME,KNAME,PKNAME,TRAN,TYPE,FSTYPE,SIZE,MOUNTPOINT
on your original system or systems when you have different kind of them.
Perhaps you may need to specify some more output columns that could be
of particular interest in case of Btrfs on multiple disks, see
lsblk -h
what output columns are available for the lsblk command on your
particular system.
By the way:
What Linux distribution and version do you use?
Cf.
https://github.com/rear/rear/blob/master/.github/ISSUE_TEMPLATE.md
ChojinDSL commented at 2019-02-05 15:35:¶
@jsmeix Here's the output of lsblk you asked for.
I use Debian Stretch at the moment.
NAME KNAME PKNAME TRAN TYPE FSTYPE SIZE MOUNTPOINT
/dev/sda /dev/sda sas disk 1.7T
|-/dev/sda1 /dev/sda1 /dev/sda part vfat 512M /boot/efi
|-/dev/sda2 /dev/sda2 /dev/sda part btrfs 1.5T /
`-/dev/sda3 /dev/sda3 /dev/sda part swap 127.7G [SWAP]
/dev/sdb /dev/sdb sas disk 1.7T
|-/dev/sdb1 /dev/sdb1 /dev/sdb part 512M
|-/dev/sdb2 /dev/sdb2 /dev/sdb part btrfs 1.5T
`-/dev/sdb3 /dev/sdb3 /dev/sdb part swap 127.7G [SWAP]
/dev/sdc /dev/sdc sas disk 1.7T
|-/dev/sdc1 /dev/sdc1 /dev/sdc part 512M
|-/dev/sdc2 /dev/sdc2 /dev/sdc part btrfs 1.5T
`-/dev/sdc3 /dev/sdc3 /dev/sdc part swap 127.7G [SWAP]
/dev/sdd /dev/sdd sas disk 1.7T
|-/dev/sdd1 /dev/sdd1 /dev/sdd part 512M
|-/dev/sdd2 /dev/sdd2 /dev/sdd part btrfs 1.5T
`-/dev/sdd3 /dev/sdd3 /dev/sdd part swap 127.7G [SWAP]
/dev/sde /dev/sde sas disk 1.7T
|-/dev/sde1 /dev/sde1 /dev/sde part 512M
|-/dev/sde2 /dev/sde2 /dev/sde part btrfs 1.5T
`-/dev/sde3 /dev/sde3 /dev/sde part swap 127.7G [SWAP]
/dev/sdf /dev/sdf sas disk 1.7T
|-/dev/sdf1 /dev/sdf1 /dev/sdf part 512M
|-/dev/sdf2 /dev/sdf2 /dev/sdf part btrfs 1.5T
`-/dev/sdf3 /dev/sdf3 /dev/sdf part swap 127.7G [SWAP]
/dev/sdg /dev/sdg sas disk 1.7T
|-/dev/sdg1 /dev/sdg1 /dev/sdg part 512M
|-/dev/sdg2 /dev/sdg2 /dev/sdg part btrfs 1.5T
`-/dev/sdg3 /dev/sdg3 /dev/sdg part swap 127.7G [SWAP]
/dev/sdh /dev/sdh sas disk 1.7T
|-/dev/sdh1 /dev/sdh1 /dev/sdh part 512M
|-/dev/sdh2 /dev/sdh2 /dev/sdh part btrfs 1.5T
`-/dev/sdh3 /dev/sdh3 /dev/sdh part swap 127.7G [SWAP]
ChojinDSL commented at 2019-02-12 10:04:¶
BTRFS is a bit unusual since it's so flexible and allows for very
unusual setups.
It's probably easier to get information about the underlying BTRFS setup
using some of BTRFS's own tools.
e..g
#############
btrfs fi show
Label: 'ROOT' uuid: 69a8d230-fe68-4504-bb14-1742acdb8967
Total devices 8 FS bytes used 2.23GiB
devid 1 size 1.51TiB used 1.27GiB path /dev/sda2
devid 2 size 1.51TiB used 1.27GiB path /dev/sdb2
devid 3 size 1.51TiB used 1.27GiB path /dev/sdc2
devid 4 size 1.51TiB used 1.27GiB path /dev/sdd2
devid 5 size 1.51TiB used 1.27GiB path /dev/sde2
devid 6 size 1.51TiB used 1.27GiB path /dev/sdf2
devid 7 size 1.51TiB used 1.27GiB path /dev/sdg2
devid 8 size 1.51TiB used 1.27GiB path /dev/sdh2
###############
btrfs fi usage /
Overall:
Device size: 12.10TiB
Device allocated: 10.12GiB
Device unallocated: 12.09TiB
Device missing: 0.00B
Used: 4.47GiB
Free (estimated): 6.05TiB (min: 6.05TiB)
Data ratio: 2.00
Metadata ratio: 2.00
Global reserve: 16.00MiB (used: 0.00B)
Data,RAID10: Size:4.00GiB, Used:2.16GiB
/dev/sda2 512.00MiB
/dev/sdb2 512.00MiB
/dev/sdc2 512.00MiB
/dev/sdd2 512.00MiB
/dev/sde2 512.00MiB
/dev/sdf2 512.00MiB
/dev/sdg2 512.00MiB
/dev/sdh2 512.00MiB
Metadata,RAID10: Size:1.00GiB, Used:71.77MiB
/dev/sda2 128.00MiB
/dev/sdb2 128.00MiB
/dev/sdc2 128.00MiB
/dev/sdd2 128.00MiB
/dev/sde2 128.00MiB
/dev/sdf2 128.00MiB
/dev/sdg2 128.00MiB
/dev/sdh2 128.00MiB
System,RAID10: Size:64.00MiB, Used:16.00KiB
/dev/sda2 8.00MiB
/dev/sdb2 8.00MiB
/dev/sdc2 8.00MiB
/dev/sdd2 8.00MiB
/dev/sde2 8.00MiB
/dev/sdf2 8.00MiB
/dev/sdg2 8.00MiB
/dev/sdh2 8.00MiB
Unallocated:
/dev/sda2 1.51TiB
/dev/sdb2 1.51TiB
/dev/sdc2 1.51TiB
/dev/sdd2 1.51TiB
/dev/sde2 1.51TiB
/dev/sdf2 1.51TiB
/dev/sdg2 1.51TiB
/dev/sdh2 1.51TiB
jsmeix commented at 2019-02-13 13:10:¶
@ChojinDSL
I know Btrfs "is a bit unusual" (polite wording ;-)
Btrfs' features just break traditional assumptions
how a stack of storage objects is usually organized
(like disks => partitions => filesystems => mountpoints).
You may have a look at
https://github.com/rear/rear/pull/1603#issuecomment-347839823
and
https://github.com/rear/rear/pull/1603#issuecomment-347860869
and follow the links therein.
I fear implementing support for Btrfs setup on multiple disks
may require that the whole disk layout code in ReaR needs
to be fundamentally changed, enhanced, and overhauled.
On the other hand
https://github.com/rear/rear/issues/2023#issuecomment-456764118
indicates that perhaps it could be even easier than it looks like.
github-actions commented at 2020-06-28 01:33:¶
Stale issue message
schlomo commented at 2024-12-13 07:18:¶
I guess we'll have to come back to this issue eventually and probably treat BTRFS more like LVM and RAID and not just like another filesystem. If we move BTRFS to the LVM / RAID layer then we could treat it as a NOOP in the filesystem creation stage.
I'd like to reopen this and mark it as waiting for sponsor, WDYT @rear/contributors ?
jsmeix commented at 2024-12-13 12:31:¶
I reopened it as a "severe improvement"
with target milestone "ReaR 3.1"
because (as far as I understand it) "ReaR 3.0"
is primarily intended to deprecate old features soon
so "ReaR 3.0" is intended to be relaeased
"relatively soon" after "Rear 2.8"
so implementing big things which take longer time
cannot be done for "ReaR 3.0".
[Export of Github issue for rear/rear.]