My laptop became very sluggish recently and I found I was getting very low on disk space. So I began the cleansing process looking for unused applications to uninstall, cleaning out my downloads folder, and finding some rarely used files/folders that I could compress to free up space. I stumbled upon a large file in the root of my C:\ drive named hiberfil.sys which was approximately 2GB in size. I didn’t know what this file was for but I figured it had something to do with my operating system. A quick Google search on the file name and I found that it is a system file which is used by the operating system to persist the current system state, including all applications and files residing in memory, to hard disk when the machine goes into hibernation mode.

The next question was do I need hibernation mode? There are two power saving modes (three if you count Shut down): Hibernate and Stand by. As mentioned above hibernation mode saves memory contents to disk, then power downs system components into low-power mode similiar to Stand by mode and can even safely shut down completely. Stand by mode does not persist memory contents to disk, all active programs and unsaved work remains in RAM and then powers down system components ( hard disk, monitor, etc)  into low-power mode. All data remains in memory as long as the system has some power. Which means, if your laptop battery dies while in Stand by mode, you’re going to lose any unsaved work.

If you decide you would like to disable hibernation mode here are the steps:

1. Open the Control Panel. ( Start -> Settings -> Control Panel )
2. Double click the Power Options Icon.
3. Click the Hibernate tab.
4. Uncheck the Enable hibernation check box.
5. Click the Apply button.

You’ve just disabled hibernation mode on your system. You may need to restart your system for the hiberfil.sys file to be removed. In my case, it disappeared immediately.

Two benefits of disabling hibernation mode:

1. I regained much needed hard disk space. The hibernation file is the same size as installed RAM.
2. My system comes out of Stand by mode much, much faster than hibernation mode. I sometimes had to wait 10-15 minutes for my machine to come out of hibernate mode. It was very frustrating.