Silly little conundrum

This isn't a problem for me, but it does pique my curiosity.

I have a pair of identical (WD20 EARS) two-terabyte data (not system) drives. One for data, the other for backup. In the root directory of each drive there are no files and only three subdirectories: $RECYCLE.BIN, LIBRARY, and System Volume Information. $RECYCLE.BIN and System Volume Information are empty (0 bytes); Library contains 1,579,923,673,786 bytes in 31,837 files, 4521 folders. This information is identical on each drive. See the attachment below for details.

However... if I go "up" one level to disk properties (as opposed to looking in root) there is a 32,251,904 byte difference in "Used space" between the two drives. This is after a full backup with "Remove deleted source files" checked, and a very rigorous defrag that took two days to run on each drive.

Is there some simple explanation of why my data drive "Uses" 32 MB more than the backup drive? Are any of you old enough to remember when 32 MB was important? Now that represents sixteen ten-thousandths of one percent of the capacity of just one of my hard drives.

tanstaafl.

Maybe these folders aren't actually empty on the data drive? (Despite what's reported)

Seems like a largish discrepancy. It can be explained (at least partially, or perhaps fully) by:

1. There's a virus / trojan hiding in there somewhere. or..

2. The drive with less "free space" used to have really big directories, and now files have been deleted from those, but not all files. So the directories are still huge, but sparsely populated. This uses "invisible" disk space like what you report.

Cheers

Windows has other files in the root of those drive that it won't show, even with all the show hidden files and folders options turned on. Odds are, the 32MB difference is in the metadata files.

http://en.wikipedia.org/wiki/NTFS#Metafiles

Hmmm... would not the de-fragging I ran take care of that?

tanstaafl.

Maybe... but since the files, directory structures, permissions, etc. on each drive are (or at least are supposed to be) absolutely identical, it seems unlikely to me that there could be 32 MB difference in the metadata. But, what do I know?

tanstaafl.

Is one of the drives attached differently? USB vs internal? I could see the 32mb difference mostly being in the journal (one of the hidden metadata files). With the USB drive, Windows may not be as aggressive with cleaning up the journal to help repair issues from the possible unplugging of the drive.

No. Both are SATA, although one of them is in an external eSATA dock.

tanstaafl.