Is it safe to use hibernate all the time?

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Summary: Hibernate is a convenient way to turn off a machine without shutting down all applications for a quick restart later.

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This is one of those theory versus practice situations.

In theory, you should be able to use hibernate all the time. In fact, I know some people who pretty much do.

In practice, however, things aren't always quite that easy.

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The theory behind hibernate is actually wonderfully simple. To oversimplify, (of course), when you hibernate the machine writes a complete image of its system RAM to the hard disk and turns itself completely off. There are two advantages to this:

• It's off. It's using no power.

• Turning it back on is faster than a full reboot.

That last point is the big appeal. It's accomplished because (once again, oversimplifying) the computer simply reloads the RAM image, and resumes from where you left off.

It actually is close to being that simple, and in theory it should always just work.

However, theory and practice don't always coincide.

There are actually several flies in the hibernate ointment. While it's definitely been getting better over time, you can still have problems.

The ability to hibernate, and standby for that matter, relies in part on support from the computer's BIOS. The problem is that some BIOS's aren't quite up to snuff when it comes to hibernate. This is, fortunately, one of the areas of greatest improvement in recent years, and is typically an issue only in older machines. Even then, it's not uncommon that a BIOS update can resolve many of the issues.

More common are issues with drivers for the various hardware that might be attached to your computer.

Let's take a common sticking point: wireless networking.

Just before you hibernate you'll likely have a working wireless connection. That connection is, of course, terminated when your machine goes into hibernation.

When you wake up or resume from hibernate that wireless connection needs to be restored from being completely powered off to whatever state it was in before hibernation. Normally, when the device is powered in it can assume that it's in a boot situation and can simply start from scratch. Unfortunately, resuming from a hibernate isn't "from scratch". The wireless connection must, if at all possible, act as if nothing happened. In addition, your computer might wake up from hibernate in a completely different location - in which case the wireless driver needs to act as if, well, something happened; something that's not quite a reboot, but certainly ... something.

It gets complicated.

And, in fact, almost every driver for every device connected to your computer somehow needs to deal with all this in ways that are specific to each device. Some, like perhaps a monitor or screen, need very little thought. Others, like network connections that need to act like nothing happened, except that the world they're connected to could be completely different, take a little, or a lot more work.

Which means that every driver is a potential point of failure for a clean resume from hibernation.

This, too, has been getting better over time, but we're certainly not living in a perfect world.

So the first answer to your question is simply this: there's nothing wrong with always using hibernation as much as you like, unless you find that it doesn't work, or that problems result. If it works, it's nifty and faster and as you said, more convenient than opening up all those applications each time you turn on the machine.

The second answer really boils down to how long you can leave Windows running continuously without a problem. Once again in theory, forever. And once again in practice: not so much. This is particularly due to applications that don't release resources the way they should - occasionally even applications that are part of Windows itself - you simply need to reboot to clean things out. How often depends on many, many things including the hardware and software installed and how you use the machine. As one data point, I'll typically leave my relatively active desktop computer running for weeks at a time.

Usually until a Windows Update comes along that requires a reboot and resolves the question for me.

If that update-related reboot doesn't come along you may find that, once in a while, you'll want to reboot .. just because.

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• Why can't my machine hibernate? And how's that different than Stand-by? Hibernate and standby are ways to save power when you're not using your computer. Each has pros and cons. Hibernation, at least, must be enabled.

• How can I keep my laptop running with the lid closed? The default configuration for most Windows laptops is to go into standby when the lid is closed. We'll look at how to change that.

• How secure is standby mode? When your computer is put into standby mode, it's turned off ... mostly. And it might wake up again on its own. Is that an added risk? Not really.

Article C3726 - May 8, 2009