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Forum Discussion
Hombibi
Aug 01, 2015Guide
Data Volume lost after disk replacement on Readynas Pro 6
Hi, I just ran into a serious problem, and I hope someone can help me. Currently my Readynas Pro 6 does not see any volume on the 6 disk X-Raid Array anymore. I walked past my NAS a couple of...
- Aug 22, 2015
Yes, required for other than windows filesystems.
Obviously much cheaper than any professional recovery service.
Hombibi
Aug 11, 2015Guide
I have decided to give it go myself.
Read a lot, found that raid/parity setups are not really good solutions anymore in these days where disks are so much larger and so different from those when these systems were created (1995-ish?). Raid 10 seems to be the current preferred setup by professionals. (no complicated expensive parity calculation, disk space is "cheap"). I further found some real good insight on recovery chances: according to one: in 85% of cases it can be solved with software, in 10% it is the circuit board, which you can even hotswap and I have 5 spare.., in 4% it is the heads or the platters, and in 1% it is the motor.
So I reckon I have a larger than 95% chance to recover my data. Worth a try.
First port of call is to make bit by bit images of the drives so that I don't have to use them for the actualy inspection and recovery of the data. I use the free linux version of r-data to make them, so that I have some idea of the chances for succes before I buy the software. I could also have used ddrescue, both these tools read the disk sequentially (as an old fashioned record) which is the least demanding for the (now fragile) HDDs.
Bought a esata hot swap cradle, filled the nas pro with 6 new disks (JBOD) and started with r-data to make images. The original disk2 (which triggered the problem) can't be read. That is a candiate for another PCB, and I could eventually replace the heads if necessary. I am currently imaging nr5, the second one that give up. Apart from a few strange noises in the early stage, the imaging process is proceeding without errors. I think that if this one works and the sixth images fine I should be able to restor the array.
I am not a pro as I stated above, any advice is welcome, to be continued.
StephenB
Aug 11, 2015Guru - Experienced User
A lot of the analysis you'll see on line about the "death of raid" is flawed. One observation is that most of the statistical analyses are grounded in the manufacturer specs, and not on real-world data.
It is true that a lot of enterprises and data centers use RAID-10. They also are often hosting storage for local VM servers, and aren't constrained by 1 gigabit ethernet network speeds. RAID-10 is faster than RAID-5 or RAID-6 - and if you aren't network-limited that performance improvement benefit can overcome the cost of the extra disks needed.
I'm sticking with RAID-5 for my main NAS myself. I am shifting to jbod for my backups, because recovery (if needed) is simpler.
Good luck with your recovery efforts - please followup (either way) on the results.
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