As mentioned in a previous article, the hibernation feature in Windows 8 can have a direct impact on your computer’s performance (as it reduces the booting times impressively), therefore, unless you are having a serious issue, it is recommended that you keep it enabled.
However, if you want to disable it (say that you’re running out of free space on your Windows partition, and one cannot move the ‘hiberfile.sys’ to another partition either. If that is the case then you can try reducing its size though), then it can be done pretty easily.
For that, please follow the below steps.
Step 1:
First, press the ‘Windows key’ on your keyboard to open the ‘Start screen’ window.
Step 2:
Then, simply search for the below term (just type it).
cmd
As you can see in the above picture, as soon as you do that, Windows 8 will find you the ‘cmd’ (‘command prompt’) utility.
Step 3:
Then move your mouse pointer over its icon and right click on it. When you do that, on the bottom of that page, a new options panel will be opened. From those options, choose the one called ‘Run as administrator’, as shown below.
Step 4:
Click on the ‘Yes’ button of the message that appears next.
Step 5:
After that, the ‘command prompt’ in Windows 8 will be opened with administrative privileges. Once it is opened, simply type the below command on its window (or you can copy it and right click on the ‘cmd’ window and choose ‘paste’ as well) and hit the ‘Enter’ key.
powercfg /h off
If it was successfully executed, then you should get a blank output (as shown above), and the hibernate file (‘hiberfile.sys’) should now be gone. That’s it.
How to get it back ?
Pretty simple. Follow the above first four steps to open up the ‘command prompt’ in administrative privileges. And then to enable it, this time, enter the below command instead of the above one.
powercfg /h on
That’s it.
How to know if it is disabled ?
Well, if you have a large RAM, then you can make a note of the disk space usage before and after disabling it. And you should see a reduction (more or less, depending on the capacity of your RAM) in the disk space usage.
Or, you can go to ‘Control Panel’ -> ‘Hardware and Sound’ -> ‘Power Options’ -> ‘Change what power buttons do’, options page.
In this page, under the ‘Shutdown settings’ section at the bottom, you will only see two options listed (‘Sleep’ & ‘Lock’), where previously it had two more options called: ‘Turn on fast start-up (recommended)’ and ‘Hibernate’.
Note: As mentioned above, please remember that, if you disable hibernation in Windows 8, then it will affect your OS’s booting times negatively. So again, unless you really have no choice, keep it enabled.

Good luck.
That cmd line to disable the fast start-up is more than perfect!
BTW im running on a SSD so it boot fast around 2-3 sec from the logo 1 spin of the circle to be precise and one should consider running that cmd once a month just to erase that hyber.sys. windows was getting slower and i didnt know why,3-4 spin to boot and since iv shut-it off than back on im back to 1 spin!
That hibernation file seems to keep a lot junk in memory like stuff that that you dont use but have use a some point and when you boot windows check to see if last time it was running and so on then you end-up with a 15-20 sec boot lol