60 - 20 = 0?

[bwbarbieri]

I have a second hard drive disk that I use strictly for storage. It's compressed in order to fit as much as I can on it. In order to make even more room, I decided to zip 60MB of files. Since there wasn't enough room on the drive to hold both the unzipped and zipped files, I zipped them to my other HD (drive C http://sysopt.earthweb.com/forum/smile.gif. Then I deleted the unzipped files (on drive D http://sysopt.earthweb.com/forum/smile.gif. Then I moved the 20MB zip file to the D drive.

When I checked how much space was now available on the D drive, I had only 6MB. This was about as much as there was before. Please explain this new math: Is 60 minus 20 really equal to zero? Where did the 40MB go?

[Additional: I checked defragmentation and re-ran Compression Agent with no result. I also checked the C drive and host drives. Nothing. And, yes, I did empty the recycle bin!]

[OuTpaTienT]

Hi bwbarbieri, I believe we've discussed drive compression before, but not as the sole topic so you might have overlooked this fact.

In simple terms, think of your compressed drive as one big zip file, because essencially that's what it is. Everything on that drive is already compressed. So trying to compress something on that drive, by Zipping it, is like trying to squash an aluminum can that's already squashed. This is why you see no difference in the free space on that drive when you Zip something.

That make sense?

[NDD]

Agreed, disk compression can't compress something that's already compressed (do I use to much "compress" word ?).

Best Regards ...