A Deeper Look at Disk Space Usage in Windows 7 (and Windows Vista)

A recent posting to the Engineering Windows 7 blog (one of our favorite sites for Windows 7 news, by the way) has some very useful information about the mysterious WinSxS directory in Windows 7 (and Vista), and how Microsoft is trying to curb Windows' appetite for disk space in Windows 7.

The C:\Windows\WinSxS folder (first introduced in Vista) looks as if it is a huge gobbler of disk space, (it uses 3.5GB of disk space on a new system, and can use 10GB or more as a system is used) but what does it do, and is that space really being "used up?"

As it turns out, both Windows Vista and Windows 7 use the WinSxS folder to point to files that are actually found elsewhere in Windows; in other words, the amount of space that the WinSxS properties sheet says is in use isn't accurate. So, what's the folder for?

By using the WinSxS folder to store what the blog calls the "installation and servicing state" of all system components, Microsoft makes it easier to roll out Vista installations with imaging technology and to patch the image offline (Windows XP and earlier versions aren't image-friendly, and require third-party tools and clunky workarounds to permit image-based deployment). Also, if you get rid of the WinSxS folder, you make it difficult to keep Windows running reliably. So, the word on the street is, "keep the WinSxS folder." To remove old files replaced by Windows Vista SP1, the blog entry provides a link to information about the command-line VSP1CLN.exe tool.

So, if the WinSxS folder is going to get bigger over time as a logical consequence of installing updates and patches, is there any way to save space in Windows 7? Some of the approaches being considered include:

• Reducing the number of drivers installed in a standard installation (Windows Vista installs around 1GB of driver files)
• Automatically removing Windows components that have been replaced by a Service Pack or hotfix
• Reducing the size of the hibernation file (hiberfil.sys)
• Providing user configuration of the number of system restore snapshots stored by Windows

Although hard disks have never been cheaper on a cost per GB basis, Microsoft is working very hard to make sure that the disk space you paid for is used as efficiently as possible in Windows 7, especially on systems that have limited disk space.