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File System Recovery

Posted: Sun Apr 15, 2012 11:13 am
by muzicman82
Hi all,

I have a OWC Mercury Elite Pro Qx2 RAID enclosure which uses the Oxford 936SE chipset. It has 4x Western Digital Caviar Black drives (2TB) in RAID5. Everything has been fine with this for a year or more. There was 1 large NTFS volume.

The other day, during it's normally scheduled Scandisk, it took forever and proceeded to do what looked like recover almost every file from something. After that, everything seemed fine. A couple days later, I noticed the drive wasn't appearing in Windows. I power cycled the drive and checked Device Manager, and sure enough it was connected. I checked Disk Management, and apparently the partition was lost. CRAP!

In R-STUDIO, it says the drive has a "Microsoft Reserved Partition" from 17kb-128MB, and then "Volume {some long id}" from 129MB-5.46TB.

So I ran an R-STUDIO scan. It found two blocks of recognized data, but neither has all of the data. Am I screwed?

I don't think this is a case of needing to do a RAID recovery since the unit mounts properly, unless that could help?

I have no idea what happened to the data. My only guess is that when I power cycled the enclosure, it didn't see a valid RAID set so it wiped and created a new one?

Ideas would be great!

Re: File System Recovery

Posted: Mon Apr 16, 2012 7:22 am
by Alt
How does Disk Manager see the RAID, as a RAW disk or with a file system, like NTFS?

Re: File System Recovery

Posted: Mon Apr 16, 2012 8:32 am
by muzicman82
It says RAW.

Re: File System Recovery

Posted: Tue Apr 17, 2012 9:01 am
by Alt
You have to disassemble the RAID and create a virtual RAID out of the disks. This article gives the overall concept on virtual RAIDs: RAID recovery presentation, this help chapter explains how to create a RAID 5: Basic RAID 4 and RAID 5 Operations, and this free program finds required RAID parameters: ReclaiMe Free RAID Recovery.

Re: File System Recovery

Posted: Tue Apr 17, 2012 9:17 am
by muzicman82
OK, I will certainly try that. Can you briefly explain why it can't be treated as one volume/disk? That's a little beyond my knowledge of how this stuff works.

Re: File System Recovery

Posted: Wed Apr 18, 2012 4:28 am
by Alt
There may be several reasons for that. One, for example, is corrupted RAID service information.
When a RAID controller creates a RAID out of the disks, it writes some service information on it like the disk order, block size, etc. When such information becomes corrupted for some reasons, the controller cannot assemble the RAID anymore, or does that incorrectly. Therefore, Windows cannot access file system information and treats the RAID as an unformatted volume. But the data on the disks remains uncorrupted and can be recovered.
When you create a virtual RAID in R-Studio, you specify those parameters manually, the RAID is assembled correctly, and the data may be retrieved.
Just notice - this is only one reason, there may be others, and it's impossible to determine which one without seeing the actual data on the disks.

Re: File System Recovery

Posted: Sun Apr 22, 2012 4:12 pm
by muzicman82
OK, I removed the drives and mounted them individually and created a virtual RAID block. I used 512 byte block size and left synchronous for Oxford 936SE. It found the same files as it did in the enclosure.

I'm guessing this means the data is hosed?

Time to start over I guess.

Re: File System Recovery

Posted: Mon Apr 23, 2012 8:12 am
by Alt
muzicman82 wrote: I'm guessing this means the data is hosed?
Most likely, yes.