Sleep, Hibernate, Shut Down?
I just recently installed Windows 8.1 on my laptop, and one of the first things I noticed was the faster boot speed. Besides that, I was also forced to select Shut Down from a menu that lists Sleep, Hibernate and Restart. As we know usually in Windows 7 we just shut down after using the PC, but now faced with such a menu, it got me curious to find out the differences between sleep, hibernation and shutting down the PC.
I love to sleep. But will your computer like it if you put it to sleep? Simply put, sleep for your PC is pretty much like sleep for yourself. Most of your body goes to rest, but your brain never ever shuts off. In the case of your PC, only the RAM will still be powered to keep the data in it intact, the other components are shut off. As soon as you wake it, your PC will start right back up, with all your open windows and files ready to be used again.
So why not sleep instead of shut down or hibernate since it will cut the boot time by so much? Firstly, keeping the RAM powered means there is still some minor power consumption. While there is some power consumed, you shouldn’t worry too much about your laptop running out of battery and you losing all unsaved data, as Windows will automatically switch to hibernation when your battery level is low.
Another feature that was added since Windows Vista is Hybrid Sleep. Hybrid sleep saves the data in the RAM to the hard disk à la hibernate mode, but also keeps the RAM powered. Hybrid sleep is actually conceived for desktop PCs that might face unexpected power failures and power supplied to the RAM will be lost, thus losing all the data in the RAM. If power is not cut, the data will still be loaded from the RAM, thus still giving the user the same speed as waking up from usual sleep mode.
Unlike sleep, hibernation is a deeper state of rest. While humans are unable to hibernate, many animals do to conserve energy. While in hibernation, they use as little energy as possible by going into a very deep sleep. For computers, it’s almost the same thing. Even the RAM is powered off.
However, like sleep, as soon as you power up your PC, all your open windows will be ready to use once again. As the RAM is not kept alive,how is this possible? In hibernate, the data from the RAM is copied into a file named hiberfil.sys in your hard disk before everything is fully powered down. When you wake your PC from hibernation, the data from hiberfil.sys is loaded into the RAM, all your open windows and files ready for you to use again.
One thing that is notable is that if you use a SSD and really care about reducing the number of writes to your precious SSD, you should not use hibernate as the amount of data written to your SSD will be equal to the amount of data on your RAM at the time you hibernate it. It will also prevent Windows from creating a file the size 75% (by default) of your RAM capacity in your SSD.
Shut down is the classic power off where the data in your RAM is neither kept on the RAM itself or transferred to the hard disk but cleared. Shut down is also a very vital function in the most used computing of all, “have you tried turning off and turning on again?”. As shut down clears everything from the RAM, naughty stuff hiding in the RAM will be cleared off as well, hopefully giving you a properly functioning PC once again. I personally have a habit of shutting down my PC everyday.
A new feature added in Windows 8 is fast startup. It utilises something like a hybrid of hibernation and shut down. Instead of completely clearing off the RAM and powering off, it clears off the user data (all your open windows), and only saves the system’s data from the RAM to the hard disk. As Windows no longer has to wait for the kernel session to load in your next boot up, it will be quite a bit faster than a conventional boot up. An advantage of shutting down with hybrid shut down over hibernate is that it will take less time since the system data is a lot smaller in size compared to the user session. Your PC should also boot faster from hybrid shut down than hibernation since the data to be loaded is also lesser. Of course the master race with SSDs need not care about this feature much.
I did some experimenting with my own Lenovo Y50 which has a i7 4710HQ, 8GB of DDR3L RAM running at 1600MHz and a 1TB 5400 RPM hard disk. With my usual workload of browsing for information with many tabs in Chrome, I filled up to 3.1GB of my RAM. The amount of RAM utilized will affect the amount of data written to hiberfil.sys file, so it will affect the hibernation results. I will test how long it takes to Sleep and wake up, Hibernate and wake up and also Shut down and boot up with fast up enabled and disabled. I have disabled the lock screen and turn off password protection. Time taken for entering sleep mode, hibernation and shutting down is measured from clicking the respective button to the moment the system lights are all off. For waking up from sleep and hibernate modes, wake up time is measured from the push of the power button to the moment the desktop is displayed and all my peripherals are lit up and ready to use. Booting time is recorded from push of the power button to the moment the Start screen is displayed. Every scenario will be tested 3 times to get an average time.
Sleep: 6.70 seconds to be fully asleep. The system woke up in an average of 2.75 seconds.
Hibernate: 18.57 seconds to enter hibernation mode. The system woke up in 23.36 seconds.
Shut down (fast startup disabled): 18.62 seconds to full shut down and 44.63 seconds to boot up.
Shut down (fast startup enabled): 17.57 seconds to full shut down and 18.41 seconds to boot up.
A caveat in this experiment is one has to consider is that after booting up to the Start screen, it still took quite some time before I could load Chrome and continue where I left off. So it takes longer to be productive when shut down. This delay was even longer with fast startup disabled.
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From my simple tests above, it shows that sleep offers the fastest speed to enter the low power state and also returned to full functionality the fastest. Booting up after shutting down with fast startup disabled took the longest and is reminiscent of Windows 7 boot up times.
So which mode to use? In my opinion, use Hibernate as much as possible since it offers all the power saving of shutting down and also has the user data maintained like Sleep mode. It also has comparable start up time versus booting up with fast startup enabled but allows the user to return to work immediately after starting up, effectively being faster than shutting down.
However with UEFI, SSDs, boot times are getting shorter and shorter. Soon we may be using PCs that will enter and exit hibernation as fast as sleep mode. One of our writers actually worry that with boot times getting faster and faster, we may not be able to press BIOS hotkeys at all in the future! However I believe we will have workarounds by then.