Windows – Why does compressing and decompressing the SSD hard drive free up space

compressionssdwindowswindows 7

I bought an SSD (SandForce 2), created a tiny 25GB partition on it for Windows and installed Windows 7 64-bit. In order to free disk space, I enabled compression on the drive using the Properties entry in the context menu for the drive in Explorer.

Prior to compressing I had around 5GB of free space. After compression I had 4GB, so compression was not working for me. I figured this might have happened because of the built-in data compression of the SSD.

I decompressed the files again – after decompression, it left me with 7GB of free space! Better yet, after restarting, I had 10GB. What is happening here?

Best Answer

Differences of 2 or 5 gigabytes are tiny. Changes in size of swap file or temporary files created by programs easily account for that much or more.

Is your pagefile of static size, or do you let OS to book it when needed? Do you use Photoshop or other program that uses lots of disk space for temporary files?

You can check the pagefile settings at "Control Panel" / "System" / "Advanced system settings" / "Performance" / "Settings" / "Advanced" / "Virtual memory" / "Change". If any of the drives lists "System managed", then Windows allocates and frees the pagefile as needed.