Improper shutdown causing data loss

[Him]

Why does an improper shutdown (Hard shutdown, or removing the power during Windows) casue data loss? I know it dosent always happen, but why are hard drives susceptible to data loss when power is removed like that?

 

[Chankama]

They are?.. I've never experienced that... :-\.. Stuff u've "saved" goes away??

 

[Him]

Sometimes, not so much in NT as it did in Windows 9/x and earlier. It used to be that if you improperly shut down your computer, you would corrupt whatever was being currently used, which was usually Windows. Thats why you always have to go to Start/Shutdown and not just press and hold the power button until it turns off. That is also why CHKDSK starts when you improperly shut down your computer. Have you never questioned why you arent suppose to shut down a computer like that? You have to learn to ask why.

 

[Chankama]

Well yeah! That i've experienced. But that's not "data loss" man. It's called "not saving the current state correctly".. Two completely different things!..

You made it sound like information on your permanent storages "gets lost".. Obviously, if u "turn off" the computer without letting it to save the state, problems will occur ..

The worst problem I've gotten is registry corruption. Doing a "scanreg" and restoring the state is usually a quick fix. Sometimes, the corruption can lead to problems with some windows drivers so not loading them, starting windows, and doing a proper shutdown, usually works fine.

 

[Him]

I'm not worried about fixing it, I know it happens. I'm just wondering why Windows, for example, would get corrupt because of an improper shutdown. Thats all. I'm talking the theory behind why it happens.

 

[Chankama]

Well, you' d have to go to the windows source code for that. Not really theory, just implementation details I would imagine.

When u save a state, typically u want it to be atomic - as in the "saving" process should only be done if all the stuff that are saved are consistent with each other and won't cause problems. Otherwise, "none" of the things should be done at all. But, it's not always easy I would imagine in an environment such as Windows. We are not talking about a simple database transaction here, where things could be "clearly" grouped together.

So I would imagine, that it just "saves" stuff, and doesn't have time to save "other" stuff to make the whole windows system consistent with each other.

 

[m3trj]

If something's open and you don't shut down properly, then it's because it was in RAM and as soon as power is lost to the RAM it clears all the data that was in it.

 

[SkyHi]

Actually, with the older computers, the chkdisk was to see if the disk had, I believe, any physical problems. I could ask my dad when I get home, he's described it to me before. But if you take the power away suddenly, the head arm (ref 1) doesn't shift correctly. Now, when the computer starts up, it reacts incorrectly. Therefore, it can give you errors, it can scratch something, etc..

ref 1 - http://www.computerhope.com/help/hdd.htm

-SkyHi

 

[vagnozzi]

If you make changes to system settings and/or installed programs, and shutdown the computer in an unproper manner, it can cause the stability of the computer to decrease because of memory settings/conflicts

Not really corruption of the hard drive, but files on the hard drive are not seen where they should be all the time, causing BSOD sometimes

 

[m3trj]

Actually, with the older computers, the chkdisk was to see if the disk had, I believe, any physical problems. I could ask my dad when I get home, he's described it to me before. But if you take the power away suddenly, the head arm (ref 1) doesn't shift correctly. Now, when the computer starts up, it reacts incorrectly. Therefore, it can give you errors, it can scratch something, etc..

ref 1 - http://www.computerhope.com/help/hdd.htm

-SkyHi

The read/write head floats on the air pressure created by the disk, which has an angular speed of about 150mph. On most newer hard drives, there is a large capacitor. This is so when power is lost to the drive, the head is automatically brought to the center of the drive where the head can safely land while the drive spins down, preventing head crash.