Rebuild of the btrfs filesystem after a complete NAS crash

[jfgratton]

Hi,

For some reason, unexplained by Support, I've lost my RAID configuration overnight, and I'm struggling to recover the data on the disks.

I've an AS6604T unit with 2x 6TB in RAID1 (btrfs). 2 bays are empty for now.

Now, the RAID has been lost for the main data partition, but I took both disks from the NAS and have put them in USB SATA docks to connect on my linux PC. I've rebuilt the disks, but am unable to rebuild the btrfs filesystem.

Here's what I do so far, and where I get blocked:

1. Check how the array is named, and which device holds the data:
root@nas:/ # cat proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md125 : active raid1 nvme0n1p4[0]
483798016 blocks super 1.2 [1/1]

md127 : active raid1 sda4[0]
5855934464 blocks super 1.2 [2/1] [U_]

md126 : active raid1 sda3[0]
2095104 blocks super 1.2 [4/1] [U___]

md0 : active raid1 sda2[0]
2095104 blocks super 1.2 [4/1] [U___]

unused devices: <none>


So /dev/md127 is the one holding my data. To be sure, I'll check what's on it, what filesystem:

root@nas:/ # blkid /dev/md127
/dev/md127: UUID="a145dc0b-05fd-4279-bbb2-746c417967b4" UUID_SUB="cc5a7fd5-0878-4fb4-8680-2305ac8ee400" BLOCK_SIZE="4096" TYPE="btrfs"


Yup.. md127 is on btrfs


So next step: fs check.

root@nas:/ # btrfs check /dev/md127
Opening filesystem to check...
parent transid verify failed on 21315584 wanted 322656 found 552839
parent transid verify failed on 21315584 wanted 322656 found 552839
parent transid verify failed on 21315584 wanted 322656 found 552839
Ignoring transid failure
parent transid verify failed on 1028620288 wanted 542391 found 545868
parent transid verify failed on 1028620288 wanted 542391 found 545868
parent transid verify failed on 1028620288 wanted 542391 found 545868
Ignoring transid failure
ERROR: could not setup extent tree
ERROR: cannot open file system


Bam, that's where I'm at. I do not know how to fix that .


Any idea ?