Compression reduces free space

[Mark]

I am running Windows Vista Ultimate and just compressed several large
directories on Outlook 2007 and under my Documents directory in Explorer.
After the compression was done, the amount of free space was less than
before. Why did this happen? Is there a trick to using compression, or a
better way to free up space?

Mark

 

[DL]

What outlook files/directories do you refer to?
The only large outlook files are likely to be the data files and its best to
comress/clean these up within outlook.

What size is C, is this your only drive & how much free space remains?

 

[Mark]

Thanks for the reply.

The outlook files are several data files that I created (e.g., clients.pst)
and I compressed them through Outlook rather than through Explorer.

C is the only drive on my computer. It is 147 GB and has 13.2 GB. To give
you an idea of what happens, I'll run through a scenario.

The drive now has 13.2 GB free.
In Explorer, I migrate to a subdirectory of my Documents directory
C:\Users\myname\Documents\Ordinances\Texas Codes. I right click the
directory and it indicates that Texas Codes is 1.6 GB and the size on disk
is 1.61 GB (I don't understand how the size on disk can be larger than the
size, but I proceed anyway).
I compress the Texas Codes directory though Explorer (I right click the
directory, go to Properties, then to Advanced, then click "compress contents
to save space," then hit "apply," then "apply to all folders or
subdirectories." The "Applying Attributes" feature runs.
After "Applying Attributes" is complete, the "Texas Codes" Directory now
shows that it is 1.6 GB and 1.3 on disk. So, it dropped by about 300 MB.
I would think that the C drive should now have 13.5 GB free. Right?
Nay-nay! Instead of INCREASING by 300 MB, my free space has now fallen to
12.7 GB. So, instead of gaining space, I LOST about 600 mb of free space!
(BTW, my Outlook program was not receiving new messages, and I saved a large
file to a USB drive, so nothing was added to my C drive during this
process).

Seems counterintuitive to me. And a bit scary. Any thoughts?

 

[DL]

Well Vista, depending on version, may be creating a shadow copy of the files
that have been 'altered'
Curently you have too little free space for efficient Vista operation, you
need 15% minimum of drive size eg 22gb.
Have you cleaned up temp files, amended IE temp files storage (to 50mb),
reduced size of restore, keeping any backups on C etc?
What size is your actual Documents (all data/music/pics etc)

 

[R. C. White]

Hi, Mark.

I can't explain compression, but maybe I can help with one small part of
your query.

it indicates that Texas Codes is 1.6 GB and the size on disk is 1.61 GB (I
don't understand how the size on disk can be larger than the size

Even a 1-byte file might take up 4 KB of space on the disk, since that is
the size of a single cluster, or "allocation unit". Just like if you have
only one letter in your mailbox, it still takes a whole mailbox because
nobody else's mail can go into that box. So a thousand 1-byte files have
only about 1 KB of data, but they take up about 4 MB of disk space (1,000
times 4 KB - using approximate numbers here). (NTFS actually can store
small files more efficiently than that, but this should illustrate the
concept.) And every file that is not evenly divisible by 4 KB will "waste"
some space in the final cluster - on average, 2 KB (1/2 cluster) per file.
For a few large files, the "slack space" is minimal, but for many small
files, it can be substantial.

RC
--
R. C. White, CPA
San Marcos, TX
(e-mail address removed)
Microsoft Windows MVP
(Running Windows Live Mail 2008 in Vista Ultimate x64 SP1)

 

[Gerry]

Mark

Where are you getting your fee disk space information from?

In Windows XP most users looked at the figures in Windows Explorer. If users
used third party file managers they also got their figures from the same
source as Windows Explorer. The figures never reconciled because the results
of file compression were ignored. Instead of using size on disk the file
size figures were taken. I would not be surprised if the same situation
applies in Vista except that you have the added complication of shadow
copies referred to by DL.

Are you using any third party backup programmes?

Have you run Disk CleanUp?

Start, All Programs, Accessories, System Tools, Disk CleanUp to empty the
Recycle Bin, remove Temporary Internet Files etc. Also select the More
Options tabs and remove System Restore Points and Shadow Copies. Please
advise what affect this has on free disk space?


~~~~


Gerry
~~~~
FCA
Stourport, England
Enquire, plan and execute
~~~~~~~~~~~~~~~~~~~

 

[Mark]

Gerry -

Thanks to you and DL for the reference to removing shadow copies - I ran
this and the computer got back up to 22.8 GB!

And to R.C. - thanks for your info. It's always interesting to hear about
the technicalities, although I find it a bit hard to follow -

Mark

 

[Gerry]

Mark

Glad to be able to help.

It would appear likely that you will need to include their removal in your
routine housekeeping to maintain a reasonable amount of free disk space.



~~~~
Hope this helps

Gerry
~~~~
FCA
Stourport, England
Enquire, plan and execute
~~~~~~~~~~~~~~~~~~~

 

[DL]

22gb free is still borderline and unless you have a large ammount of data
something else is consumming space.
If you are creating backups on this drive there is little point since if the
drive goes west so do your backups.
You perhaps should be considering installing a second drive.