I was contacted the other day by a friend who had mysteriously lost over 400GB of disk space on his Windows Machine’s C drive. He seemed to be losing about 30gb a week. Most odd.
I checked the files sizes on the disk and he was only using about 90GB of the 500GB space but CHKDSK was showing 490 used.
After some research I discovered he was showing about 500 entries in the Previous Versions tab of the C drive. These are usually the result of System Restore points and this seemed a lot.
I then ran up a command prompt as administrator (Right click Command Prompt Run as Administrator) and used the VSSADMIN tool to analyse the situation.
vssadmind list shadowstorage
This shows what storage is being used for Restore Points. Usually this is limited to 15% of the disk but in my friend’s case it was set to Unbounded and was using 400GB
vssadmin resize shadowstorage /for=C: /on=C: /maxsize=20GB
To reset the maximum size used to 20GB.
I then ran disk cleanup and chose more options
The clean up option in System Restore and Shadow Copies removes all but the latest restore point.
After doing this I was expecting the space to re-appear but it didn’t immediately. It seemed to take about 5 minutes to sort itself out but then magically over 400GB of free space appeared.
How the setting had become unbounded in the first place I do not know but changing it certainly has a dramatic effect.
I know some people like to keep more restore points but at least you can choose how much space you want to reserve.