Know your RAID level

One ReadyNAS owner seems to be confused about what RAID level is (and was) used on its ReadyNAS Duo (full story).

I have a readyNas Duo with 2x 1Tb disks in raid. … I had to reset the NAS, unfortunally i holded the reset button to long so the disks are wiped clean….

After the reset i upgraded to the latest firmware and let the disk sync.

… is my data lost, or are there way’s to recover the data?

i tried to recover my data with [RecoverMyFiles] …without success…I checked only one disk since i wanted to have the other one as an backup to be examined by a company … [and they] … think my disks were not in mirror but in striping mode…I can’t check this ofcorse but i never saw more totall space then the size of one disk.

This looks real bad. There are two things we know for sure:

  1. this is ReadyNAS Duo, and
  2. there are two physical drives.

and that’s all. There are four conflicting bits in the above quote relevant to the RAID level.

  1. [did] let the disk sync suggests RAID1. RAID0 does not need any kind of sync.
  2. wanted to have the other one as an backup indicates owner’s belief that the array is RAID1
  3. company … thinks … striping mode, that’s pretty straightforward.
  4. never saw more totall space than the size of one disk, which again points to RAID1.

Problem is, it is fairly easy to recover data either from a RAID0 or from a RAID1. Home NAS Recovery, as one obvious example, can work either way, and does not even need to know the RAID level beforehand. However, if the initial array was RAID0, and then after a reset the NAS switched to RAID1 mode and copied contents of the one disk to the other disk, there is nothing left to recover.