Wednesday, February 26, 2020

Copying corrupted files

It's been ages since I've posted anything in here, and mainly that's because I've been quietly doing the "salaried employee thing". But I did have something here I need to share.

I had a large (3TB) external drive go wonky on me... it's been very sketchy about performance and started corrupting files. So of course the first thing I did was buy another drive (which I should have done in the first place, using one for backup... but often mechanics have the worst cars...

Then I started backing up all the files I could, and came upon some that were corrupt and could not be copied by normal methods. All attempts yielded an "Error splicing file: Input/output error" message, which Linux support forums advise is due to this:
The problem is because your destination disk (the disk to which you want to copy the file) is formatted with FAT32 (which has a file size limit of about 4GB. The solution is to format your destination disk to EXT3, EXT4, or NTFS (if you need windows compatibility).
This advice in this case was absolutely incorrect. Not only that, but these days it's almost certain to be incorrect on any device, as nearly everyone now uses NTFS in the Windows world. 

In my case, it was plain old bad sectors. But I did find a free utility that works right past the problem: Roadkil's Unstoppable Copier. It's got a version for damned near any Linux or Windows platform. It doesn't need installation. And it just works. It'll try its best to read information from damaged sectors, and if it can't it will just move on and get information from the next sectors, filling in the blanks. It's good enough to have recovered a damaged .WAV audio file, and the only result of having 40 bad sectors was some scratchiness in the resultant playback, which nevertheless 1) worked; and 2) was good enough to understand what the recording was about without loss of actual high-level content. The ability to pull even partial "lost" data can be a career-saver, and may be a cost-effective alternative to sending a drive in for data recovery. At the very least, the ability to view partial data is valuable in determining whether you should spend money on professional data recovery.

It's a great program. Just get it.



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