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Forum Discussion
ReadyNAS RN214 corruption on BTRFS
4x4TB in X-RAID, holds about 4TB in daily data and 1TB in daily snapshots. Used to work fine, when suddenly last Saturday it crashed. The shares disappeared. In a move to find a solution (and since I'm very familiar with Linux), I opened ssh access and I logged in with ssh. dmesg was reporting corruption on the roots of BTRFS on md127. It does not reported hardware problem with the hard disks thought. It seemed a software issue (corruption) with btrfs.
I googled it a lot and tried whatever I could find in order to solve it. After hours on working with btrfsck, I managed to be able to "see" the filesystem on the device, but now, after reboot it reports: "BTRFS error (device md127): qgroup generation mismatch, marked as inconsistent" and mounts md127 (with the snapshots) read only.
I tried to fix it with a couple of btrfsck commands without success. The data are there and I can read them. I can take them a backup (I already have the data on an USB disk).
The best solution is to find a way to fix the corruption on md127 as it is now.
Alternatively I was thinking to factory reset it and then restore configuration and data. But in this case I will need a way to backup (and then restore) the snapshots also, but as snapshots and not as data copies. Maybe something like "format a big enough external USB in btrfs and do this and that to take a full backup - with snapshots- on it, and after factory reset, restore from it. But I'm not sure how to do this.
Any ideas ?
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Thank you for the hints. Actually I have tried all of them with mixed success. I managed to mount the system read only and copy all of the data and some of the snaphots. When I tried to get all of the snaphosts the device consistently crashed (and it was not a low memory issue because I had created an extra 4GB swap file on an extrnal hard disk to avoid low memory problems that appeared since the beggining). No matter how many time I btrfsck the system there was no other issue than the qgroup one, which I failed to overcome . Indeed this was the reason why the filesystem was marked as inconsistent and was mounted read only.
Anyway, I could not aford folling around anymore, so I took backup whatever I could and I factory-reset it.
Thank you for your support.
Now seeing this same issue after trying to move disks from a RN516 to a RN526X (see my two related posts).
L3 support has been more than USELESS (and not a soul based in the US, apparently). What is a synonym for "more than worthless", Siri?
The data is still there. I can tell.
Advice? The volumes are currently in the RN516. Last L2(?) tech said it was IMPOSSIBLE. Admin console and SMB unavailable, though Radar still sees the volume.
Hi roryt,
Thank you for sharing your resolution and/or workaround. We appreciate your contribution to the community.
Feel free to post any suggestions, questions, recommendations or anything about your NAS that you think needs attention or will help others.
Regards,
You can use btrfsck to scan the whole volume to detect whether there is any other error in filesystem level.
If you could mount the file system read-only, you could do something as simple as an rsync to your destination.
Additionally, you could also use btrfs restore to dump files (and snapshots, if you want them).
Also, qgroup generation mismatch, marked as inconsistent essentially means your quota table has inconsistent data (btrfs qgroup show /data). String together the mount command and then try btrfs quota disable /path/to/mount (mount /dev/md127 /data; btrfs quota disable /data;) and see if it still throws your ReadyNAS into read-only. Typically, an inconsistent qgroup mismatch will not be the root cause to your file system being marked read-only, it is what comes after btrfs tries to scan your system to recuperate what was inconsistent back to consistency that will cause it to be marked read-only (from experience).
If you format one (or more) USB drives as btrfs, you should be able to do what you want with btrfs send and btrfs receive. Since each share is it's own BTRFS subvolume, you should be able to use multiple USB disks.
The only catch I see is on the restore - if the readynas database needs records of the snapshots, they might not show up in the web ui. Hopefully that's not the case. Maybe a netgear person (perhaps mdgm-ntgr or kohdee) can comment on that.
Thank you Stephen for the ultra-fast answer, it gives me a road to follow, I had seen the commands but I had not realized what they were doing. So, let me see if I got it ok:
1) Format a -let say -6TB USB disk in btrfs and mount it (let say to /media/USB_HDD_6)
2) I'll use something like
btrfs send /data/daily -c /data/daily/snapshot/c_2016_09_24__00_00_19 -c /data/daily/snapshot/c_2016_09_30__00_00_00 (and so on for all of my 30 snapshots) | btrfs receive /media/USB_HDD_6
3) Factory reset. Restore configuration. Maybe make my shares again from scratch (I have only two and only one has snaphots)
4) Restore form USB with something like:
btrfs send /media/USB_HDD_6/data/daily -c /media/USB_HDD_6/data/daily/snapshot/c_2016_09_24__00_00_19 (etc etc for all snapshots) | btrfs receive /data/daily
and I'm good to go ?
Exactly. There might be some snags (though I've read about these commands I haven't actually used them).
On 3) you should definitely recreate your shares, since they need to be in the ReadyNAS database.
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