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Manual RAID-5 reconstruction possible?
I have a hardware RAID system who's controller went berserk. It's now
convinced itself that two disks are bad in a RAID-5 configuration; I would
lay heavy odds that this is not the case. One drive may for sure be bad
(though I can recover it with virtual certainty), and the other one is known
to be good. The controller went into its nondestructive rebuild mode,
forgive my ignorance, I'm not sure what to call it -- I presume it was
beginning to restripe or recalculate parity info or something along those
lines? It failed during this process due to the bad disk. Now it's
completely hung (it basically thinks two drives are bad, disaster for a
RAID-5 as far as it is concerned).
I've spoken to some of those data recovery outfits, they all claim better
than a 90% likelihood of recovery, the hitch is they want $10 - 20k to do it.
Our research group cannot afford such a bill at the moment, so I'm looking
to investigate what I can do on my own.
The companies basically claim they will do the following:
Image each of 8 disks (or at least 7).
Take the new "working" images, hang them off their own system. Run some
magic proprietary software which rediscovers the layout, destripe and get
the data backed up onto another media.
The question is this: if I do the above, get a working copy of the 8 disks
and hang them off a Linux system that can handle 8 drives, can I do something
in Linux to manually recover the data? (I've already imaged the disks myself
with dd conv=noerror,sync, got all 8 drives no problem, only one had bad blocks on read, and only on a small portion of the suspect disk) Is it possible to
rediscover the "layout data" (for lack of knowing what it is really called,
lots of reading to do!) in cases where it is completely missing? (I know the
drive order, but past that have no clue.) The system had 8 drives, a
hardware raid made by Maxtronic known as the "Arena Industrial Rackmount II"
in RAID-5 configuration, had an ext2 filesystem on it. How
manufacturer/controller specific would the layout be? Do I have a chance,
or is footing a huge bill for a recovery company my only option?
Seems like if I could figure out the striping and rotation order I could write something for myself to go and get each range of data in the right order and manually destripe myself by writing it back to a single, contiguous image. I found a post on slashdot where someone said that it was pretty easy to do, heck I could even do it with a script and dd I would imagine, but how do you figure out where everything is?
Any pointers would be monumentally appreciated! A company called Runtime Sofware appears to have a product called "RAID reconstructor" for $99 bucks which claims it could do it, which I would gladly spring for, but it only works in Windows, which I could do if it works but the problems seems 100% solvable in Linux if I only had a brain... I'm amazed at the charges of these recovery companies, how can they charge $10k for something another company can sell you software to do the same thing for 100 times cheaper? I asked one, they say it's the manhours that costs so much; then I asked how long it would take -- they said 48 hours. Hmmm, something doesn't add up...I seriously doubt they have 100 engineers working on it for 2 days straight.
Thanks,
^t
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