Fast Startup is a feature in Windows 8 and 10 which speeds up the boot process significantly. With Fast Startup enabled by default, when the user shuts down the computer, what happens under the hood is a hybrid shutdown sequence.
When a user issues the shutdown command, all user accounts are logged off completely. Then the system hibernates at this point — writing the OS kernel image and loaded drivers to the hiberfil.sys file, located in the root of your system drive (typically C:).
Powering on the computer again would cause the hiberfile to be loaded, restoring the previously saved image of the Windows kernel and loaded drivers. That’s how Fast Startup works. This way, boot ups are faster when compared to the traditional shutdown & cold startup.
Hiberfile (hiberfil.sys) type can be set to “Full” or “Reduced”. In “Full” mode, which is the default setting, hiberfile size would be 40% of the total physical memory.
Note: In Windows 7, the default size of the hibernation file is equal to 75% of the total physical memory.
Whereas in Reduced mode, hiberfile consumes disk space that equals to only 20% of the RAM.
Reduced mode is sufficient if you need the hiberboot (Fast Startup) feature, but don’t have the necessity to put the device into (full) hibernate mode manually. It helps to set hiberfile to “Reduced” if you’re running short of disk space on the system drive.
|Hibernation file type||Default size||Supported power states|
|Full||40% of physical memory||fast startup, hybrid sleep, hibernate|
|Reduced||20% of physical memory||fast startup|
Set Hiberfile type to Reduced or Full, using Powercfg
Open an elevated Command Prompt window. Type the following command and press ENTER.
powercfg /h /type reduced
You won’t be able to put your system to Hibernate mode manually when hiberfile type is set to Reduced — the “Hibernate” command wouldn’t even show up in the Start menu as well as in the Win + X menu.
If you later decide to revert to the default setting, which is Full, use this command:
powercfg /h /type full
Fast Startup feature, which utilizes hiberfil.sys, doesn’t work if you’ve turned off hibernation altogether using the
Powercfg.exe /hibernate off command.
About the author
Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and has a vast experience in Windows — delivering support for Microsoft's consumer products. He has been a Microsoft MVP (2003-2012) who contributes to various Windows support forums.