RAID Parameters

Discussions on using the professional data recovery program R-STUDIO for RAID re-construction, NAS recovery, and recovery of various disk and volume managers: Windows storage spaces, Apple volumes, and Linux Logical Volume Manager.
JMik

RAID Parameters

Post by JMik » Wed Apr 20, 2011 8:07 pm

Hello,

I was hoping someone might shed some light into a bizarre problem I'm having. First, a quick backstory. I have (or had) a 7.2TB RAID-5 array (5x2TB drives) running on a 3Ware 9500S card, with a single NTFS partition. Recently, I made the mistake of applying a hard drive firmware update to these drives, which apparently clipped the drive IDs and rendered the array unidentifiable to the 3Ware controller, even though the actual drive data remains untouched. LSI attempted to help me reset the array, but they couldn't quite figure it out, so I'm trying a manual recovery instead using R-Studio. I would have loved to follow your "Finding RAID parameters" article, but as my MBRs are all messed up, that won't work.

Here's the main problem: I've arranged the 5 disks in a Virtual Block RAID in the order I believed was correct, set the block size to 64K which I also believe is correct, and performed a full scan of the drives (which took over 10 days!). However, all of the detected files are still coming up corrupt. I tried rearranging the drives and the block order a number of times, to no avail. So going back to my original settings, I kept playing around with it until I noticed something: a particular PNG file where the top tenth (or so) of the image was intact, which I recognized as a webcomic I had downloaded once upon a time. I recovered it and compared it to the original.

My results showed that the first 94 sectors (48K) were identical, but afterwards none of the data matched anymore. This had me really puzzled, since if I've understood correctly, 64K blocks should be written continuously to each disk, right? So I figured maybe I had remembered wrong, and that the block size was actually 16K, and that I was seeing the first three drives in order. But when I set the block size to 16K all the files became corrupt again.

So, obviously I'm missing something. Am I not understanding how RAID 5 stores its data? If I set the block size to 16K, do I need to rescan all the disks? Is there some other issue? Any and all help would be most appreciated. Thanks!

Alt
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Re: RAID Parameters

Post by Alt » Thu Apr 21, 2011 8:18 am

I need some time to think the situation over, but here's an important advice.
* You don't have to scan the entire disk set, only the first 3-5 GB, because, as it seems, the data on disks are not damaged, the only problem is with the order of data blocks. When scanning the beginning of disk set, you can find the MFT, and that's enough to recover data.

JMik

Re: RAID Parameters

Post by JMik » Fri Apr 22, 2011 8:42 am

Thanks for your efforts, but I ended up figuring it out. Seems my array was Right Asynchronous for some reason, although I'm not sure why that produced the results I found. Cheers!

JMik

Re: RAID Parameters

Post by JMik » Fri Apr 22, 2011 8:45 am

Sorry, I forgot the mention the important bit: I had understood that when you rearrange the disk order or block order, R-Studio updates itself instantly. But, really, you do have to perform a new disk scan to properly re-read the sectors. You might want to make a note of that in your FAQ.

Alt
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Re: RAID Parameters

Post by Alt » Sat Apr 23, 2011 4:02 am

JMik wrote:Sorry, I forgot the mention the important bit: I had understood that when you rearrange the disk order or block order, R-Studio updates itself instantly. But, really, you do have to perform a new disk scan to properly re-read the sectors. You might want to make a note of that in your FAQ.
I think, we should add that reminder on R-Studio itself.

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