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Just installed a 60GB OCZ Agility 3 SSD, put Windows, and other various applications on there. All working fine. However, when I look at the drive in Windows 7, it says that I have 1.5GB free, but when I select all folders on the drive and view the properties to see the combined file size it says that the total is 28.9GB. So I'm effectively losing half of my capacity!!

Any ideas on what this could be?

PC Spec:

Windows 7 60GB OCZ Agility 3 SSD

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Did you install new RAM memories ??? Check the Paging File... – user131919 May 3 '12 at 1:42

If you are checking the free space by selecting the folders, you are doing it the wrong way.

The correct way is to right click the drive and select Properties. *The Pie graph is correct. *

Even more correct is going to Computer Management under Admin Tools and selecting Disk Management.

I'm pretty sure there is an obligatory Old New Thing blogpost about this.

The long technical explanation has to do with security. When you select all folders and use Explorer to calculate the space, Explorer is adding up all the files and giving you size.

  • But what if Explorer can't see certain files?

Windows hides certain files from Explorer for a couple of reasons. One is for organization and a streamlined user experience. The second is to keep users from breaking their own systems. If you go under Tools/Options, there should be a check box for hidden files and protected operating system files. If those are checked, then selecting all folders obviously isn't going to select all files that exist.

Other caveats include Explorer does not add the size of alternate data streams, ever.

The pie graph, 99% of the time, is correct. The only big factor you worry about is that the pie graph is constrained by your user quota, if it exists. Selecting files and right clicking for the size was never meant to be a definitive answer. Not so much a case of Explorer was lazy, but it isn't the right tool for that job.

I hope that helps.

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Thanks, you would imagine Microsoft would be logical and traverse the tree! However, after taking note of David's answer below, when running WinDirStat, which traverses the tree there is a hidden portion labelled as "Files" with a 15.9GB pagefile.sys and 11.9GB hiberfil.sys - this is obviously where my capacity is going. Any ideas what these files are, and what can be done to get my full 60GB back!? – Chris Nov 21 '11 at 0:04
pagefile.sys is your virtual memory, hiberfil.sys is needed for hibernation. You do not need that much virtual memory or maybe even none at all depending on how much physical memory you have. Also, if you never use hibernation, you can deactivate it and get rid of the second file. – Dennis Nov 21 '11 at 0:25
@Chris: Traversing the tree is not a reliable method of determining disk space usage and free space, for the reasons I posted above. Plus it is I/O intensive and again, an unreliable method considering the structure of the file system NTFS. It's not laid out like a book shelf. I guess the best analogy is a post office. Behind each post office box and mailbox, there is a undetermined number of people. A post office box could be used by a whole firm. Until you thoroughly investigate each branch of the tree, you can't assume. The pie graph is from the file #bitmap. – surfasb Nov 21 '11 at 4:28
This file is literally a bitmap of every cluster mapped on your drive. The pie graph comes from that file. Traversing folders is like determining how many free parking spots are in a parking lot by asking everyone in the building if they parked outside. Some may have parked outside. Some may have rode together. Some may have parked on another log. Some may have taken up two spots. The other route is to ask the Security booth how many spots have been taken up today. – surfasb Nov 21 '11 at 4:33
@Dennis: I'd at least leave a small pagefile, like 3GB. But I agree 16 is way too much. No pagefile is a bad scenario that leads to random app crashes, or more than likely, bluescreens. I also agree if you don't hibernate, then you can safely delete the hibernation file. – surfasb Nov 21 '11 at 4:56

If you realy want to do it that way (wich is kind a 'unproffesional'), you should first enable 'Show hidden files and folders' in the Folder menu in Windows.

The problem is probably your Pagefile (C:\pagefile.sys), or Hybernate file (C:\hyberfil.sys).

These are normally 1 to 1.5 times the amount of your RAM. So if you have, let say, 4GB RAM, you'll have a pagefile and a hyberfil of around 8 - 10 GB...

Page file can be disabled/deleted in the Memory menu in Windows, execute the command to disable the hybernate function, wich will automaticly delete hyberfil.sys:

powercfg.exe -h off
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Two possibilities:

  1. You have more than one partition on the drive or have unpartitioned space. Check in the Disk Manager.

  2. You have lots of hidden files or directories on the drive. Check with WinDirStat.

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