Synology: Access data on Synology SHR

Having a reliable disks and redundancy on a Network Attached Storage (NAS) is important. But when your NAS dies and suddenly can't access the files on any of the disks is a shocker. How I overcame that shocker and got access on that files.

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The good thing was: There was no urgent need to get on those files. The NAS did not die - the disks were only swapped with some bigger ones. Also there were multiple backups. But exactly this is the right time to check if you could access the files if you needed it.

So I connected one of the drives of the RAID-1 to my PC (Gentoo Linux with kernel 5.18.0). With the OS Synology DSM 7 and a 2-disk Synology SHR you will see the following: a mdadm raid containing a LVM2, containing a btrfs file system. The raid was detected automatically and the device was /dev/md127. Also quick lvs command showed directly the logical volume with the designation vg1000 - nice! Let's set it active with lvchange -a y vg1000.

The last step would be to mount the btrfs file system. So lets do that:

mount /dev/mapper/vg1000-lv /mnt

Well that did not work. The only thing I got is errors of corrupt leaf. Well... I tried a lot and there was no way to get it back to work. After some tries, repair attemps and testing the other drives of the array I checked the kernel version of the NAS. A uname -a returned:

Linux i-nas-05 4.4.180+ #42218 SMP Mon Oct 18 19:17:56 CST 2021 x86_64

Well. So it would perhaps be worth a try to spin up a live usb with an old linux kernel and give it a shot.

Yep, that was it: With a MX Linux 19.3_386 with kernel 4.19.0-12-686-pae everything mounted flawlessly and I could access all the data.