Windows NTFS Compression : Decompress Entire Volume

Windows NTFS Filesystem Compressiopn: Uncompressing An Entire Volume

I recently came across a perofrmance issue on an old x86 WinTel server, The issue, after regular diagnosis showed no obvious cause, appeared to be that the root drive was compressed in order to increase available disk space.

The one problem with NTFS compression is this: 

‘When you open a compressed file, Windows automatically decompresses it for you, and when you close the file, Windows compresses it again. This process may decrease your computer performance'(http://support.microsoft.com/kb/307987)

Using the COMPACT command line tool it is possible to both identify all compressed files within a folder and its subfolders. This can be acheived using the command:

compact /I /S

To uncompress all files (assuming you have enough free disk space to do so) you can use the following command to uncompress all compressed files within the current folder and all subdirectories:

compact /U /I /S

After disabling file system compression on the root drive the server is now performing as-expected.