Corrupt File Recovery

File corruption sometimes only causes a minor amount of information loss. Other times, it can prevent a file from functioning entirely. Files become corrupt when parts of them have become damaged or the tools needed to read them break down. It’s like tearing the pages out of a book. If you tear out enough pages, or even just one important page, the book stops making sense. Gillware Data Recovery offers financially risk-free corrupt file recovery services if you have lost a critical file to corruption.

How Do Files Become Corrupt?

Our data recovery engineers here at Gillware draw a line between two types of file corruption. This distinction is based on the root cause of the corruption. One is what we refer to as “soft” corruption. The other is “hard” corruption.

Soft Corruption

“Soft corruption” is what our corrupt file recovery engineers refer to corruption that appears as a symptom of a larger issue. Fixing the larger issue will make most, if not all, of the file corruption vanish. Fixing the larger issue may be extremely difficult. But the corruption is easy to fix. More or less, it goes away by itself once the problem is fixed.

Take, for example, a hard drive with failing read/write heads. The heads can read data intermittently. Maybe one or more of the actual heads in the headstack has failed, and the rest work fine. If one of those heads is dead, you end up with “bad sectors”. These sectors aren’t intrinsically bad. There’s nothing physically wrong with the platters themselves.

But large files are often split between different surfaces of the hard drive’s platters. Because of this, it takes the combined efforts of several heads to read the whole thing. If one of those heads is bad, the file will appear to be corrupt because parts of it are unreadable. After our engineers get into the hard drive and replace its heads, we can usually read most or all of those “bad” sectors. Suddenly, the file isn’t corrupted anymore.

Soft corruption can also occur in RAID arrays. Take the example of a failing RAID-5 array. On March 24, 2016, the RAID controller card notices that one of the hard drives in the array is lagging behind. It’s still functional, but it seems likely to fail soon. Because RAID-5 has one hard drive’s worth of fault tolerance, the controller takes the drive offline and goes about its business.

But then another hard drive fails a few months later, on June 15. The entire array crashes. Your IT technician might look at the RAID and see that the first drive to fail can be brought back online. They might force that hard drive back online. The problem is that the controller stopped writing data to that drive several months ago. We refer to the first drive to fail in a RAID-5 array as a “stale” drive.

corrupt file recovery
An illustration of how data can be corrupted when a failed RAID-5 array is incorrectly

If the RAID array gets resuscitated like this, it will try to integrate all of the stale data into the array. This means that just about all of the data written to the array since the first hard drive failure will be corrupted. A file you haven’t touched since January will be fine. Your main Outlook PST that’s seen constant use since March won’t be so lucky.

This makes RAID data recovery more difficult for our engineers. It creates massive amounts of file corruption. Repairing the second failed hard drive and using it to reconstruct the array without the stale drive can clear a lot of it up.

In file corruption data recovery scenarios, we call these types of corruption “soft”. File corruption isn’t the problem in and of itself. The real problem is usually a much more serious issue. Clearing up that issue tends to fix the vast majority of the corruption.a

Hard Corruption

“Hard corruption” is a different matter for our corrupt file recovery engineers. This type of file corruption has a root cause, but addressing the root cause will not undo the corruption. The corruption itself has to be addressed.

Take a hard drive with damage to its magnetic data storage platters. The magnetic coating on its platters stores all of the data on the drive. If parts of that coating are damaged, those sectors are gone forever. Sectors can go bad as a result of old age. Even if the heads are fine, those sectors are still lost. Files that have lost sectors become corrupted, and may be completely nonfunctional.

Hard corruption can also appear in files after deletion or drive reformats. When you delete files from your computer or reformat your hard drive, that once-occupied space is flagged as “unused”. As you continue to use the hard drive, more data is written to it. This data will eventually start overwriting the old data. There is no way to “roll back” a sector on a hard drive’s platters once it has been overwritten. Hard drives only keep backup sectors of extremely important things, such as firmware modules and partition superblocks.

A software crash can also cause hard file corruption. Perhaps you’ve had Microsoft Word freeze on you in the middle of a Word document. You tell Windows to force shut down the program and then try it again. But when you open the file again, Word spits out an error message. When the program crashed, it accidentally wrote some data where it shouldn’t and garbled up your document.

Other culprits for hard corruption include virus attacks or sudden and improper computer shutdowns. If system-critical files become corrupt, it can prevent your operating system from starting up altogether.