Archive for June, 2012
Hibernation, Sleep or Shutdown – Power mode options
When you’ve finished with your computer there are actually several options for the state that you can leave it in. The various options have pros and cons in terms of startup time, power consumption and memory usage.
Leave it on
You may be running a specific service or application on your computer that requires it to be left on all the time. Some business IT departments require work computers to be left on at night for doing backups and desktop maintenance. Under these circumstances, you may have no choice but to leave your computer on.
I’ve heard some people tell me that leaving computers on actually saves power because the computer hardware is more stressed than when starting up and shutting down than it does if it’s left on. The fact of the matter is that it does use more power to leave a computer on than any other alternative. And the stress on the components during startup is no more than the stress incurred on a computer when doing resource intensive tasks it will be asked to do during the time it is on anyway.
Shutdown?
Shutting down is the complete and full way to turn off your computer. All the services and applications are closed (usually gracefully) and the computer is completely turned off. Your session and the documents or programs you were working on are not retained – but this can be good if looking to reset your session. And no memory is tied up in the process. Once shutdown, the computer no longer needs external power but the startup will take longer because it has to start windows from scratch.
Pros:
- System is completely shut down.
- Only very minimal power is used while shut down for some optional services such as wake-on-lan.
- No additional hard drive space is required.
Cons:
- Session state is not retained.
- Startup times are longer.
Recommendations:
Use Shutdown if you are going to be away from your computer for a long period of time.
Sleep
Sleep is a temporary mode where the current state of your session – all the windows, pages, applications etc you have open – are saved to ram (temporary memory) and the rest of the computer is turned off. This saves on power as extra components such as your fans, hard drives, monitor etc aren’t using any power. But the computer requires a small amount of power to keep the ram alive and keep your details in the ram.
Sleep mode is very fast to resume from because ram is very fast. Typically a session can be restored in a few seconds. The main downside is that the computer must have a permanent source of power and will drain some power over time. If a laptop is running on a battery only in sleep mode, it will drain the battery and eventually, when the power gets low enough it will go into hibernation mode (see below).
Windows can perform maintenance tasks while in sleep mode and network adminstrators can still wake and access sleeping computers to perform backups or do system administration tasks. Some workplaces may require employees to leave computers in sleep mode overnight for this reason.
Pros:
- Fast resume time
- Session state retained
- Computer can still perform maintenance and be accessed remotely if set up.
Cons:
- Requires a small amount of permanent power – will not work for desktops if the power is unreliable or not available for the entire sleep period.
- Can drain a battery to zero if left for long periods of time – time varies depending on the size, age and quality of the battery and the power drain of the laptop.
- Doesn’t reset the computer so any resources are not released as they would be during a shutdown or reset.
Recommendations:
Use sleep if you are going to be away from your computer for a short period of time or if you have a network or computer administrator that requires it.
Do not use if you are on a desktop and can’t guarantee a consistent power supply or on a laptop if it is going to be on battery power for an extended period of time.
Hibernation
Hibernation is a tradeoff between shutting down and sleep mode. In this mode, your session is saved to your hard drive and then the computer is powered down. In this state the computer does not require any external power because the state is saved to the hard drive. The computer will resume from this state faster than when it is shut down completely but not as fast as sleep mode. This mode requires you to have some free space on your hard drive for saving the session state.
Pros:
- Does not require any power while in this mode.
- Session state is restored
- Startup is faster than a fully shut down computer
Cons:
- Cannot be accesses or perform maintenance tasks
- Startup is slower than sleep
- Requires some hard drive space set aside for saving session state to hard drive.
- Hibernation file can become fragmented and occasionally corrupt over time but restarting can usually resolve this.