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I don't know if this is a Windows Vista-specific trick, or maybe something related to Volume Shadow Copy (the service that supports System Restore), but there seems to be a major discrepancy on my hard drive.

In Windows Explorer, open the C drive, select all, then Alt+Enter to open the properties dialog.

Size: 128gb (137,787,853,411 bytes)
Size on disk: 129gb (138,600,678,813 bytes) (Note: I don't know how there's an odd number of bytes, except that apparently NTFS uses some type of odd clustering strategy - to my knowledge, the "size on disk" field should be a multiple of 4,096, the default NTFS partition cluster size for this size disk).

Now I navigate up to My Computer, right-click on the C drive and choose properties.
Used space: 267gb (287,193,178,112 bytes)
Free space: 664gb (713,020,395,520 bytes)

(This drive is a RAID-0 stripe of two Maxtor 500gb SATA drives)

Now if I set it to display protected OS files and folders, I can come up with a few new items:
4gb in hiberfil.sys (Hibernation support)
4gb in pagefile.sys (Virtual memory swap file)
132gb in \System Volume Information (System Restore)

Looks like I've discovered the reason for the space usage - System Restore.  Ugh.  Hard to believe I've had this installation of Windows active for about, what, not even a week?  And System Restore has managed to take up more space than the files I've installed.  The good news is, with it set at 15%, I'll probably only get another 7gb taken.  Still....  It's just incredible to me that it's filled so fast.

Posted on Wednesday, January 2, 2008 12:51 AM | Back to top

Comments on this post: Where Have All My Gigabytes Gone?

# re: Where Have All My Gigabytes Gone?
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It is the Shadow Copy feature in some versions of Vista. The unforutunate thing is that you can't turn off this feature without turning of the system restore feature.
Left by Don Demsak on Jan 02, 2008 4:12 AM

# re: Where Have All My Gigabytes Gone?
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yes, but you can reduce the amount of space you want Shadow Copy to use on your HD. more info here:
Left by tgo on Feb 13, 2008 2:43 AM

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