Re: Defrag increases "used space" as reported by command-line defr
- From: HMT <HMT@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 19 Jun 2009 13:34:01 -0700
The simple way to recover this lost space is to turn System Restore off and
on again. By the way, when you turn System Restore on in Vista, it does not
automatically create a Restore Point as with XP. You must create a Restore
Point manually - something Microsoft should fix. I just discovered the same
problem as Mike after running defrag c: -r, then defrag c: -w from the
command prompt. I lost 3.6GB the first defrag and then lost another 1.75GB
the second defrag. After turning System Restore off and on, my free space
went from 16% to 41%. This seems like a bug to me - Microsoft, please fix.
HMT
"mwhiting001@xxxxxxxxxxxxxxxxxxx" wrote:
Victoria, I echo Rock's thanks. It is a relief to know that the growth is.
limited. I looked at your reference, followed some of the links, and
concluded that the additional space is used for a restore-point in case data
are damaged in the move. Also, thanks for the awareness of other sources of
info. provided by links in the referenced blog. Thanks to everyone who
replied, too.
Mike
"Rock" wrote:
"Victoria House [MSFT]" <vhouse@xxxxxxxxxxxxxxxxxxxx> wrote
"mwhiting001@xxxxxxxxxxxxxxxxxxx" wrote in message
Why does defrag increase the disk's "used space"? This happens with both
the
GUI version, and the command-line version. The command line flag "-w"
results in a greater decrease in used space. I used (command line)
defrag c:
-a -v to generate a report, ran the GUI defrag, and then reran a report.
It
seems that the GUI version repeatably increases "used space" by about .7
GB.
The "free space" value sometimes doesn't show a decrease, due to the
lower
precision of the number (no decimal values), and the amount of
fragmentation.
The command line version increased "used space" by 1.37, for each of two
runs that for which I saved the analysis report. The "free space" value
IS
reduced for the more aggressive defrag:
"defrag c: -w -v. Is this additional used space usable, or is it lost
forever, or until the disk is reformatted?
See
http://blogs.technet.com/filecab/archive/2007/01/26/don-t-judge-a-book-by-its-cover-why-windows-vista-defrag-is-cool.aspx
The blog says that defrag attempts to prevent copy-on-write by the Volume
Shadow copy Service (VSS) where possible.
Whenever this is not possible to prevent, VSS's diff space will increase,
decreasing available free space.
The space is not lost forever, it is being used to back up your files that
have "changed" according to VSS, due to their being moved around by
defrag.
vssadmin.exe will tell you about your shadow storage space. There is a
default maximum allowed shadow storage space (15% of volume), so you
needn't fear your free space decreasing until there's none left.
Thanks for the explanation, Victoria.
--
Rock [MS-MVP User/Shell]
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