Sleep Versus Hibernation

April 21, 2010

A computer basically has four possible power states it can be in. On, Off, Sleep (also called standby and suspend mode), and Hibernation. On and off are pretty obvious, so we’ll concentrate on the other two.

SLEEP

When a computer goes to sleep, power is cut to almost all components of the computer except the memory (RAM). The memory will continue to use power to keep the information in memory. When the computer comes out of sleep, the other components are powered up and the computer will be just like it was before it went to sleep. So if you had a web page open, for example, that web page will still be there. Anything else you had running will still be there.

Advantages
Although it still uses power, it saves power compared to when the computer is turned on. When the computer comes out of sleep a lot faster than if the computer had to start up after being turned off. So it will be ready for you to use sooner.

Disadvantages
Windows XP doesn’t handle sleep mode very well. When you come out of sleep on an XP system, there are often networking issues, display issues, and other issues that can make it quite frustrating. Another disadvantage is that when your computer is asleep, it may not be able to perform certain activities. Your security software may not be able to update itself and clean your computer. You may not be able to access your computer remotely. These and other automated tasks that normally run when you aren’t using  your computer may not be able to run when your computer is sleeping. These tasks will either not get done, or they will run when you are using the computer which will slow it down.

Recommendation
We only recommend sleep mode for laptops when on battery power, but not on AC power.

HIBERNATION

We saw how sleep keeps the information in memory alive and shuts down all other electrical components in the computer. Hibernation, instead, takes that same information in memory and writes it to the hard drive and then turns off the computer. So the only real difference between sleep and hibernation is where the information is stored.

Advantages
Unlike sleep, hibernation doesn’t use any power because the information is stored on the hard drive. That is really the only advantage hibernation has over sleep. Hibernation has an advantage over turning off your computer in that it is faster, although not as fast as sleep, and everything you were doing on the computer will still be there.

Disadvantages
Hibernation has the same disadvantages of sleep. In addition to those disadvantages, hibernation has additional disadvantages. Because hibernation has to write the information to the hard drive before going into hibernation and read it from the hard drive when coming out of hibernation, it is much slower to go in and out of hibernation than it is for sleep. It’s still faster than shutting down and turning on a computer, but not much.

Advantages
Hibernation has the same advantages as sleep does plus one more. The big advantage to hibernation over sleep is that it doesn’t use any power.

Recommendations
Like sleep, we only recommend hibernation for laptops on battery power.
 

RECOMMENDED POWER SETTINGS

Now that you understand sleep and hibernation, here’s what we recommend.

Go into the control panel. In Windows XP, click on “Power Options”. For Vista and Windows 7, type in the word power. Then click on the green “Power Options”.

Vista and Windows 7 have power plans. You can select one of the preconfigured power plans or you can create your own. XP just has power settings  you can set.

For a desktop, we recommend you set it so that it never sleeps and never hibernates. You can set it so that the screen will be turned off after a certain period of inactivity. How long is up to you. On Vista and Windows 7 you can even tell it to turn off the hard drive and other components after a certain amount of time. Doing that is OK too.

For a laptop,  you can configure it to act differently depending on whether the laptop is running on AC power or battery power. For AC power, we recommend setting it up just like a desktop. That way, you can leave the laptop plugged in and turned on from time to time and it will do all of that maintenance.

For battery power, we recommend that you have the screen turn off after 5-10 minutes along with the hard drive if you have Vista or Windows 7. We recommend you have the computer go to sleep after 15-30 minutes of inactivity. We also recommend you have it go into hibernation after 1-2 hours of hibernation. Basically, the sooner you turn things off, go into sleep mode, and go into hibernation, the more power you save and the longer your battery will last. But you have to balance that with usability.

So you could configure your laptop so that when it is running on battery power, after 5 minutes of inactivity, it will turn off the monitor and the hard drive. After 15 minutes of inactivity, you could have it go to sleep. Then after 1 hour of inactivity, you could have it hibernate. So if you stopped using your computer at 3:00, at 3:05 it would turn off the monitor and the hard drive. Then at 3:15 it would go into sleep mode. Then at 4:00 it would go into hibernation.

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