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I'm a Windows 8 user, and I've got 2GB RAM. I noticed the following phenomenon:

  • When hibernate is disabled, the pagefile.sys will be the same
    size as my RAM.
  • But when hibernate is enabled, the size of pagefile.sys will be only about 25% of RAM and hiberfil.sys 75%.

It's easy to notice that the sizes of pagefile.sys and hiberfil.sys add up to the size of RAM, whether hibernation is enabled or disabled. We know that the hiberfil.sys is used for the hybrid boot of windows 8. In other words, it's only used for boot process and becomes useless after the system booted. My guess is that windows 8 just reuses hiberfil.sys as another part of pagefile.sys when the system is already on. I'm looking for an authoritative answer on this.

So, why does the size of pagefile.sys decrease to only 25% of the RAM when hibernation is on?

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"Now the interesting thing is that when you have fast startup enabled (meaning hibernation is enabled), then your hiberfil.sys will be about 75% of your RAM and the paging file will be around 25%. This is because the hiberfil.sys contains the Windows 8 kernel and device drivers. The paging file is only used if all RAM is exhausted only our system and is used while you’re actually running Windows. The hiberfil.sys is only used for the boot process.

If you don’t have hibernation enabled in Windows 8, you’ll see that the paging file is now the same size as the amount of RAM you have."

More details:

Windows 8 hiberfil.sys and pagefile.sys details

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This article just refers to the phenomenon as "an interesting thing". It still doesn't explain why the system needs a pagefile of the same size of RAM when hibernation is off while needs only a pagefile of just 25% RAM when the hibernation is on. The pagefile.sys is used as an extension of RAM when the RAM is exhausted in both scenario. So what's the difference? – ltux Mar 25 '13 at 19:25
I think that depends on the point of view and that it does explain it - from the text above, the hiberfil will contain your drivers and kernel - thus the paging file can be smaller – TomEus Mar 25 '13 at 21:13
I'm sorry, but I can't make sense out of this. The statements This is because the hiberfil.sys contains the Windows 8 kernel and device drivers. and The hiberfil.sys is only used for the boot process. seem contradictory to me. – Dennis Mar 25 '13 at 21:26

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