Question RAID5 Array Recovery?

Alachas

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May 29, 2009
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Hi everyone. I'm pretty sure I already know the answer to this one, but I thought it best to get another opinion, particularly from someone which much more knowledge than me!

I have a RAID5 array with 3x 4TB HDDs (so 8TB of storage). About a month ago one of the drives failed. The only error I could see in SMART was that the "Current Pending Sector Count" was 7. So I powered down the system, physically disconnected the failed drive and restarted. The RAID array showed as "degraded" (obviously, because it was missing a drive), but I was still able to use the RAID drive. I realise that I was being risky by still using the drive in this fashion, but I had some files on it that needed to be accessed by other users, so didn't really have the luxury of leaving it completely offline. I had ordered a new HDD and had hoped that it would arrive quickly and I could just swap out the dead drive and then rebuilt the RAID array with no issues.

Anyway, while my new HDD was on its way, a second of the drives failed. This time with a "Current Pending Sector Count" of only 1.

Now, obviously with two failed drives, a RAID5 array is broken, but I'm wondering how "dead" the two drives actually are? Like, is it still possible to recover any data from them? The "Current Pending Sector Count" values seem to be quite low. The first disk that failed has a "bad" health status in Crystal Disk but the second failed disk is only showing as "warning", which makes me think it might still be potentially recoverable?

Fortunately, I did do a complete back-up only a fortnight before the second disk failure, so worst case is that I lose 2 weeks of data, but I would obviously much rather recover as much as possible before resorting to that (I will incidentally be replacing all of the drives with a single 10TB shortly).

Any advice that can be provided would be greatly appreciated and please ask any questions that you might have that could narrow down my options.
 
The single pending sector suggests that one sector is unreadable and is waiting to be replaced with a spare. I would clone that particular drive with HDDSuperClone or ddrescue, and then run data recovery software against the clone and the remaining good drive.

DMDE (US$20) can assemble a virtual RAID and recover your data. If you only want a few files, the free version of DMDE can recover up to 4000 files from any one folder per session.
 

Alachas

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May 29, 2009
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The single pending sector suggests that one sector is unreadable and is waiting to be replaced with a spare. I would clone that particular drive with HDDSuperClone or ddrescue, and then run data recovery software against the clone and the remaining good drive.

DMDE (US$20) can assemble a virtual RAID and recover your data. If you only want a few files, the free version of DMDE can recover up to 4000 files from any one folder per session.
Thanks for the suggestion. I will check it out and see what I can get!
 

Alachas

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May 29, 2009
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Yes you could try ddrescue on the drive that shows the pending sector count, clone to the new drive and if you’re lucky it will come back. However might be a good time to think about Dropbox or one drive. Or at least raid 6.
This system is pretty old and I'm in the process of getting a new one, which won't require any RAID arrays, it will just be a single 1TB SSD and a single 10TB HDD. My back-up drive is 4x 10TB HDDs in RAID10 (doesn't support RAID6 or I would have done that).
 

TommyTwoTone66

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Apr 24, 2021
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Well I don't know how valuable your 2 weeks of data is, but if you're anything like me its a few TV shows and movies you can just download again anyway.

Recovering the data to any meaningful extent is likely to take many hours of your time and once recovered, the files will be in a jumbled mess and not necessarily correctly named or in the directories they should be in.

Unless its some work you need to get back, and there's no guarantee you will, don't bother with recovery.
 
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Alachas

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May 29, 2009
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Well I don't know how valuable your 2 weeks of data is, but if you're anything like me its a few TV shows and movies you can just download again anyway.

Recovering the data to any meaningful extent is likely to take many hours of your time and once recovered, the files will be in a jumbled mess and not necessarily correctly named or in the directories they should be in.

Unless its some work you need to get back, and there's no guarantee you will, don't bother with recovery.
Most of it is just TV shows, etc. I'm not worried about that stuff because the logs of what I have downloaded are stored on my SSD and are intact, so I can just re-click the links.

But I had also been doing quite a bit of video editing and whatnot, too (not for work). So it's not critical that I get it back, but it would certainly be preferable.
 

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