How come Hibernating doesn't need power?

Today after I put my X220 to Hibernate, I forgot it was on Hibernate, and I unplugged the power cord, then went out. Some 3 hours later after I came back, I realized I had unplugged it while it's on Hibernate, so I thought I must need to restart the computer. Howerver, after re-connecting the power cord to the laptop, and pressing the power button, the computer was back on just like it was on Hibernate. I logged in and there was no restarting at all.

So I'm curious: how could the computer not shut off when the power cord was completely removed? )Note: there was NO Battery in the laptop.)

 

True hibernate saves what is in memory to a hibernate file on the drive. It then fully shuts down. When you turn it back on it can resume by loading everything back into memory from the drive

I takes no power so you could resume weeks later and it would be right where you left off.

 

Wow, thanks, didn't know that. So is there any advantage to shut down the machine at all, as opposed to Hibernate? especially relevant to the longevity/lifespan of the laptop?

 

Depending on use and OS, shutting down and doing a clean boot will be faster than using hibernate.

I personally hate hibernate and my Thinkpad is only hibernated when it passed the S3 > S4 timer when on battery. Otherwise it's either on, shut down or in sleep (S3)

 

I agree with above poster. Ten years ago hibernate was great, when machines had 512MB memory and it only took a few seconds vs the minute or two to boot up. Nowadays a full boot may only take 15-20 seconds from an SSD and hibernating with 16GB ram can take longer than that, plus it uses up valuable SSD space assuming the OS is on an SSD.

I also like doing clean boots, you have less chance of problems for programs when they start up fresh each time.

That being said, if hibernating is quicker than a clean boot for you, and it hibernates fast enough for you, go ahead and use it. I would still recommend you fully shutdown once and a while though. I know if I didn't I would end up with programs not working properly or drivers crashing.

 

Thanks. But my top concern is the life of the computer. I don't care waiting for more minutes. Which way is better for reducing the wear and maximizing the computer lifespan?

 

I don't have any evidence to support either outcome, but I don't think it hurts the components to do a hibernate if that is what you are asking. The memory and hard drive, and the computer itself will not notice and discernible change in life expectancy based on your use of hibernate ( In my humble, un scientific opinion) I just think a better user experience is the full shutdown and startup.

 

When hibernating vs shutting down I get a lot more disk activity; but that SSD will be worthless anyway before it stops working due to wear.

As for hibernated vs shut down once done: it doesn't matter at all.