btrfs driver unable to mount RAID 1 volume

[kallisti5]

Attempting to mount a raid 1 btrfs volume results in an error:

KERN: btrfs: [524642679:  2316] Failed mounting the volume. Error: Invalid Argument

mount -ro /dev/disk/usb/0/0/0 /VOL01
mount: Invalid Argument

Theoretically it should be mountable as read-only

[kallisti5]

From Linux:

$ btrfs fi df /VOL01
Data, RAID1: total=647.00GiB, used=640.71GiB
System, RAID1: total=8.00MiB, used=112.00KiB
Metadata, RAID1: total=1.00GiB, used=769.80MiB
GlobalReserve, single: total=512.00MiB, used=0.00B

[pulkomandy]

Can you check if the partition contains a RAID superblock: ​https://raid.wiki.kernel.org/index.php/RAID_superblock_formats

You have to check for the value 0xa92b4efc at either the start, 4K bytes after the start, or somewhere at the end of the partition (you can check that in DiskProbe for example).

If that's the case, we can probably add a "partitioning system" that recognizes this partition and re-publishes its content (without the RAID superblock) as a mountable partition.

[kallisti5]

Nah, no software md, or raid blocks. RAID's are handled internally within btrfs.

$ ls /dev/md*
ls: cannot access '/dev/md*': No such file or directory

Disk /dev/sdc: 15628053168 sectors, 7.3 TiB
Model: 728T8TALE6L4    
Sector size (logical/physical): 512/4096 bytes
Disk identifier (GUID): DEADBEEF-DEAD-DEAD-BEEF-CAFE
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 15628053134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048     15628053134   7.3 TiB     8300  Linux filesystem