When System Restore was introduced in Windows XP (and less famously, in Windows Me) in 2001, there was concern over how much disk space the System Restore repository was consuming.
By default, XP allocated a maximum of about 15% of the space on any given volume for System Restore, but the user could change this amount through the System Restore tab in the My Computer | Properties pane. Many users elected to turn System Restore off entirely, especially on non-system drives.
With Windows Vista, however, the System Restore tab (now called System Protection) doesn't let you configure the amount of disk space used by System Restore (or Shadow Storage as well). It's an all-or-nothing affair: You can either leave it on for a given drive, or turn it off entirely. Again, the default allocation for the store is 15% of a given volume's free space.
So what's happened? In the seven years since Windows XP came out, drive sizes have exploded. In 2001, 40 to 80GB was the high end of the storage capacity you could expect to purchase with a new computer; today, 500GB to 1TB is not unheard of. Microsoft's philosophy is that using 15% of 500GB (or even 250GB or 160GB) is far less onerous for the average user than using 15% of 80GB was in 2001.
But this probably won't sit well with people who want to have some level of control over the size of the shadow volume on each drive. The good news is that while the GUI for the System Restore volume sizing function has vanished, the command-line utility vssadmin does the same thing. So an administrator can easily write a batch file or some other script to accomplish the needed changes to the shadow volume in an automated way.
To use the vssadmin tool, you'll need to run an elevated command prompt. The syntax for changing a given drive's shadow volume size is:
vssadmin resize shadowstorage /on= /for= /maxsize=
<drive_letter> is the drive letter to change the storage parameters for; <max_size> is the maximum size with a suffix that designates which units you're using (typically MB or GB). If you typed vssadmin resize shadowstorage /on=c: /for=c: /maxsize=2GB, this would resize the shadow volume for the C: drive to 2GB. The changes should take effect immediately.
Note: When you change the size of a shadow volume, it's truncated so that the oldest entries in the volume are deleted first. Also, if you leave off the /maxsize switch, this allows the shadow volume to grow without limits. However, the /maxsize setting can never be less than 300MB for any volume.
About the author: Serdar Yegulalp is editor of the Windows Insight, (formerly the Windows Power Users Newsletter), a blog site devoted to hints, tips, tricks and news for users and administrators of Windows NT, Windows 2000, Windows XP, Windows Server 2003 and Vista. He has more than 12 years of Windows experience under his belt, and contributes regularly to SearchWinComputing.com and SearchSQLServer.com.
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