I have (or at least, I think I have) an adequate backup setup on my computer. Data does not get get added/updated all that frequently, and there is no data that would be life-altering if I lost it. Inconvenient, yes, but if (for example) I lost all my music, I have the original CDs. There are pictures I wouldn't like to lose, but if I did, well, life would go on. With that said, I probably do my backups about once a month.

My C: and D: drives are my Windows and data drives, respectively. I back up to my E: drive, and also to an external USB drive at G:. My music, in addition to being on my D:, E:, and G: drives, is also on my empeg, so with four complete copies I feel reasonably safe. (Yes, Paul G. no doubt has his music on at least six different empegs as well as his system backups , but I know my limitations!)

So, I ran my backups last night, and then started doing file size comparisons, source to backup. There seem to be discrepancies.

If I right-click the C: drive and select properties for the whole drive(where I get the pretty little blue and pink pie chart) it shows a considerably different amount of used space than if I use Windows Explorer and highlight all the directories and show properties there. The D: drive does the same thing, but to a much lesser extent.

When I look at the used space on the backup files, I get more discrepancies yet, with the backup files only taking about 2/3 the space of the source files on the C: drive, and about 90% of the space of the source files on the D: drive.

There are even small differences comparing the E: backups to the G: backups, and they should be identical. Shouldn't they?

I know that some of the discrepancies are related to files in use in the Windows directory that can't back up. But nearly six gigabytes difference? (see table below) Doesn't seem likely. And why would there be a difference of more nearly nine gigabytes in C: space used when looking at the "whole drive" (with the pie chart) and the files on the drive?

When I ran the backups, all recycle bins were empty, compression was not turned on for any drive, and backup filtering was set to *.* (backup all files) with no directories or files excluded.

....................TABLE OF USED SPACE...................
.
Whole Drive.......Files on Drive......E: Backup#1.....G: Backup#2
==============================================================
C: 37.766 GB.....C: 28.912 GB.....E: 24.139 GB...G: 24.182 GB
D:158.302 GB....D:158.071 GB....E:158.055 GB...G:158.950 GB


Oh, Doh! A bit of super-sophisticated highly technical sleuthing on my part (I compared the file lists of source drive to the backup drive) shows two very large files on the source drive that are not on the backup drive: hiberfil.sys, and pagefile.sys. Hiberfil.sys I can safely get rid of. Pagefile.sys I think I'll keep. Uncle Google says I can kill it if I really need the space as long as I have lots of RAM, but with "just" 2 GB RAM (I remember how excited I was when I spent $400 to upgrade my old 386 computer to four MB of RAM!) I'll leave it be. I was mostly just interested in why my backups were so much smaller than my source, and that explains a lot of it.

I'm still confused about why my "whole drive" used space is so much more than my "files on drive" used space, though.

tanstaafl.