hibernation vs sleep

what are the pros and cons of each of the above? when do you prefer one over the other?
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Jason Yousef, MSSr. BI  DeveloperCommented:
That's easy...
 Hibernate takes a snapshot of everything you got on RAM (including any  windows and apps running) and saves it to a special hard disk file and  then shuts the computer down, when you resume from hibernation the  computer boots a bit faster than a normal power up bootup. This method  does not consume any power while the computer is off.
 Uses: When you are not going to use the computer for a few hours or more.
 Sleep, basically shuts your computer down except some components like  RAM, so the next time you resume, it will boot almost in an instant.  However, this method consumes battery power.
 Uses: When you are just leaving the computer for a few minutes or hours, like at lunchtime or something like that.
 I usually use Hibernate when I go to sleep or come back in more than an hour, so I can save Hard disk time, as hard disks get measured by hours used,  I hope I helped you clear that up a bit.


No power used
System memory saved to a file
Recovery from hibernation is considerably longer and more problematic returning to normal use

Sleep Mode
Minimum power used
System memory is retained
Applications are retained
very fast recovery to normal use

Personally, I never, ever use hibernation and disable it from all my systems. I allow sleep mode only. It is well worth giving up some power loss during sleep mode as opposed to the potential problems hibernation can bring.

One other note... If left in sleep mode long enough to fully drain the battery, or if ac power is lost when running without a battery, all work is lost.
Gary CaseRetiredCommented:
Personally I don't use either ... but I'll offer a few comments on each:

(a)  Hibernation.    As noted above, hibernation saves the entire state of the computer to a special file (hyberfil.sys), then turns the PC off.        When Windows boots, it looks for a "hiberfil.sys" -- if it finds it, it restores the state of the PC from that file.     One major advantage of hibernation vs. sleep is that since hibernation is really just OFF with a special state file, all hardware devices get re-initialized during the boot process ... just as they would if you had simply shut the system down without hibernating.     Hibernation is very reliable, since it's a full reset for all the hardware, but with modern systems there's little difference in the time it takes to resume from hibernation and the time it takes to simply do a normal boot.    Since I never leave open (unsaved) work on the desktop, there's no reason to use it.

(b)  Sleep.   Sleep usually refers to what is more accurately called "S3" state (there's another sleep state known as S1).    In S3 the system turns off the video adapter and hard disks, and suspends the CPU.    Power is retained for the memory and possibly the USB ports (depending on the settings).    When you press a key the system "wakes up" and is ready to use in just a couple seconds.     One issue with S3 is that many hardware cards do NOT support S3 and will often not work correctly after the system has been in S3 ... some video cards and many specialized cards (TV tuners, video capture cards, etc.) are well known for this.      Consequently, you need to test YOUR system to see if all your hardware "plays well" with the S3 mode -- if so, it's fine to use it;  if not, I'd avoid it.     Even if it works, I wouldn't use it unless your system is UPS-protected, since you can lose work if you have open files and the system is in sleep mode when you have a power failure.

I prefer to simply leave the system on, with the video set to shut down after a few minutes (I use 15) and the hard drives set to spin down after an hour ... this mode uses more power than S3, but is ready faster (virtually instantaneously on a keypress), and does not have any of the issues associated with S3.
Sleep mode is a low power state. If your computer's power is cut while it is sleeping, it's nearly the same as just pulling the plug while it was running (although at least the hard drive shouldn't be running if the computer is sleeping).

Hibernate writes RAM to disk then powers off the hardware. It is normally much faster getting back to the desktop from hibernate than it is from a cold startup (here, about 15 seconds vs nearly a minute and a half)

Hybrid sleep, new starting with Vista, is a combination of the two. It writes RAM to disk like hibernate but then only sleeps instead of powers off. If power is lost here, it resumes like it would if it was hibernating all along.

If you are going to use power saving modes, I recommend sleep and hibernate on battery power and hybrid sleep on AC power... although that is a very general recommendation..

a different strategy may be better for some computer uses or usage patterns.. for example, our "work" and "gaming" computers are shut down and powered off when not in use. Since they are never left idle for more than an hour or so at a time (about how long it takes to grab a lunch or make a beer run), we don't have power saving modes enabled on them.
anushahannaAuthor Commented:
Very pertinent info. Thanks experts.
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