I'm looking for some help about the fundamentals of the storage technology used by the ReadyNAS Duo, in order to perform a data recovery, or a way to restore the ReadyNAS Duo without erasing existing data.
Summary of the situation
a) Data were lost.
b) The RAIDar software (installed on Windows) was not able to detect the NAS when connected via an Ethernet wire.
c) The left drive shows a table of Linux partitions. I assume that the data are on /dev/sdb5, which is described as a Linux LVM.
d) The right drive does not show any partition table.
e) I was told that some kind of reset may have been done, which could have affected storage.
f) I could clone both drives at low level and no error was reported. Hence, I assume pure logical corruption.
My questions
1) Is RAID-X very similar to RAID 1, so that I could perform the data recovery on only one drive or is there on the contrary some interleaving between the two hard drives?
2) Should both drives contain a partition table, or is the RAID implemented in such a way that the partition table on the first drive suffices?
3) Is there a way to mount the LVM volume with Linux (and possibly perform a filesystem check at mounting)?
4) Is there a way to restore the content on the NAS (typically some "resynch")?
5) Is there a way to restore the Linux system running the NAS (for instance reinstalling) without destroying the data, or to make a full reinstall and then bring back the partition data from the clones (typically with ddrescue)?
a) How do you mean data was lost? Can you describe what happened that led you to this conclusion
c) and d) With X-RAID on the Duo v1, it is normal for only one disk to have a partition table on it. In this case disk 2 is the dedicated parity disk which does not have a partition table on it. Newer models use distributed parity across all the disks and don't have a dedicated parity drive.
e) Told by whom?
1) You could do it on just disk 1 (the one with the partition table).
2) Only on one of the two disks in the Duo. See comment above
3) Assuming the data is still there, this may help: http://home.bott.ca/webserver/?p=306 - I assume you still have the clones? These could be useful if something goes wrong with attempting data recovery.
5) If I have a remote look at your system in a low-level diagnostics mode I may be able to give an answer on that.
a) Files were no more accessible. Some backups were disapeared before the things worsened and the NAS became undetected. This is why I tell about data loss, but of course I hope to recover the files.
e) The friend to which the NAS belongs to, as he tried a few things on its own after the problem occured. I'm not sure what happened exactly.
3) Sure that I'll keep the clones in a secure place. Thanks for the link who gives me hope ; I'll try.
5) I should ask permission for this. I'll try 3) first but may contact you again later if it does not suffice.
3) Assuming the data is still there, this may help: http://home.bott.ca/webserver/?p=306
When above link is down, you can still find the page with the WayBackMachine: https://web.archive.org/web/20140711191324/http://home.bott.ca/webserver/?p=306
I followed the four first steps of the procedure mentioned by the link. Using CentOS, they were no available rpm packages. Furthermore, compiling from source lead me from problem to problem due to lacking dependencies. So I used Ubuntu (like in the procedure) and it was easy to install the binary packages at steps (2) and (3).
At the step (5) of the procedure "vgscan" give no result at all. Just a message telling that the scan could last a while. The drives were within the NAS, which was connected through an Ethernet wire. Should I have use an USB wire instead?
Also, at the step (7) of the procedure, I don't understand what "/dev/c/c" mean. I'm familiar with "/dev/sda1", a.s.o, but not with the "/c/c". What does it denote?
Thanks a lot for your support ; I read about LVM and could mount the logical volume.
The folders are here, but all are from long time ago. The friend who I'm trying to help remembers having done some kind of reset and it's now like the NAS was restored to the status of one of the very first backups.
So, I currently need some way to seek for the file structure before the files and folders were removed.
As some data recovery tools are not able to work with logical volumes, I'm considering cloning the (non-mounted) logical volume to another drive. Just after step (6) of this procedure: https://web.archive.org/web/20140711191324/http://home.bott.ca/webserver/?p=306 Then, I plan to use a recovery tool for ext3. Would this work?
I wonder if the free R-Linux, applied to this clone, would suffice, or if R-Studio for Linux would be required. I'm also considering using ReclaiMe (running on Windows), especially if was possible to make the logical volume directly accessible to it.
I would like to avoid using Photorec and such tools, as I need the folder structure to be kept.
Not sure about your ideas, but you could give them a try and hopefully you will be able to let us know what works for you.
Could be hard to get the data back (if even possible) let alone keeping the folder structure.
Not knowing what "reset" your friend did does make it difficult to assess the situation.
Please encourage your friend to backup important data primarily stored on the NAS in future. No important data should be stored on just the one device.
