So I have two 3TB HDDs, one being the backup of the other, almost full (containing mostly videos, TV documentaries and whatnot), with no hardware issues (SMART parameters are all fine). I plugged one of them through an Akasa Integral external enclosure, in USB 2.0, to my laptop PC running on Windows Vista. The HDD was erroneously detected as being 746GB, and a CHKDSK analysis was recommanded, supposedly to avoid data corruption ; I didn't think twice and let it run... but then, I quickly discovered that it had severely corrupted the file system : a comparison with WinMerge showed that more than 100GB of files were damaged to a varying degree (for some of them only a cluster had been replaced or overwritten, some were entirely wrong and unreadable, for some of them the begining was in fact the begining of another file of any other type – for instance a MP4 file appeared to have a MHT header, or a TXT file appeared to be a directory index, etc.). Doing another CHKDSK analysis on my desktop PC running on Windows 7 with the HDD directly connected in SATA did not repair those files. Luckily I did not lose any important file as I had a virtually complete backup, but still, I'd like to understand what happened and why.
Now, what happened here ? Is it a known issue ? Could it be due to a limitation of the USB controler of that external case ? Normally Windows Vista is supposed to deal with 3GB HDDs just fine (as opposed to anterior versions). I think (but I'm not sure) that I previously used that same external case to plug a 3TB HDD to that same laptop in eSATA with no such issue.
And can someone help me understand how CHKDSK could corrupt the file system, although it's precisely supposed to ensure that it stays consistent and perfectly operational ? What did it do to the MFT to get that result ? Did it consider that any cluster beyond 2TB, was invalid and had to be un-allocated ? Yet I couldn't find any particular pattern with regards to the location of the affected files : most of them had been added recently, but some of them were older, having been copied in bulk when migrating from a smaller capacity HDD ; some of them appeared to be at the end, some at the begining, way before the 2TB mark (I used WinHex and R-Studio to find out the locations).
Any hint would be appreciated, thanks !
