Zip subterfuge

Microsoft caused me a pretty major headache this morning…

I was re-arranging some computing resources on my home network, and I decided to ZIP up some files before sending them across a slow 100BaseT connection. (Well, slow when you’re talking about my home file server… around 320 gigabytes of data.) So I zipped up a few shares, each between 5 and 20 gigabytes each. Microsoft’s built-in Zip functionality took forever with this data, but after a while, it finished. The software was basically telling me “OK! I’m done! Go ahead and delete the originals, secure in the knowledge that you have a nice safe, secure archive.


I moved the archives over to another system, and re-formatted the original drive. Then I tried to unzip them to their new home… and I got an error saying that the zip file was corrupt… I was horrified. All that data! I have week-old backups of everything, but I would HATE to have to deal with a restoration! So what went wrong?

Well, it turns out that the ZIP format only supports archive file sizes up to 4 gig… something WinZip, Stuffit, and other decent Zip compression implementations will tell you if you try to create a file that exceeds that limit… but not Microsoft’s implementation.

No… theirs just pretends like it finished successfully. It basically flushes your data down the toilet without telling you anything is wrong. Here’s the admission straight from the horse’s mouth. (Or, given my current mood, straight from the horse’s ass!)


All wasn’t lost though… I downloaded Advanced Zip Repair, and it got about 99% of my data back without a hitch. Saved me from spending 6 or 7 hours restoring a third of a terabyte from backup.

However, that doesn’t get Microsoft off my shitlist… a bug like that is unforgivable.