Will using a laptop in a car or bus cause any problems?

Sometimes a car or bus will shake a lot while traveling, and I was wondering if this would cause any problems for a laptop while it is being used, such as damage to the harddisk, or damage to the disk drive if a cd or dvd is spinning inside it. Does anyone have any experiences with this?

Thanks.

How ya doing, buddy?

I think most modern drive now have a acceleration sensor, so they can detect if the harddisk is moved rapidly (like when your drive is falling down from a high place). In case the acceleration is above some predefined threshold the parking mechanism kicks in a navigates the sensitive head to a safe place.

Now that's the theory. In practive this should work, BUT we don't know the exact threshold when the mechanism is activated. I doubt it will do it if only light shaking is occuring.

What I'm thinking about (what could become a problem) is powersaving mechanisms, that do nearly the same thing as the G-sensor. Moving the head in parking position and slowing down the drive spindle.

Recently I bought a new laptop drive, a 160GB Samsung 2.5" harddisk which supports way more ATA command stuff than my previous Hitachi drive. I can adjust noise level (this affects the drive rotation speed) and APM (advanced power management) and a lot of other things. Why do I mention this?

I had some kinds of "problems" after installing the drive and transferring my data back. I noticed a lot of clicking noises when the drive was not used (linux filesystem caching is very impressive with 2GB of RAM, you get almost zero drive activity when doing normal work). It was a frequent clicking, like every 5 seconds. And sometimes it was like a clunking sound. I was afraid... afraid of my new drive and the data that was now residing there.
So I did a SMART check. There you have a counter named "load cycle count". That counter counts how many times the head has gone into parking position and left the parking position again (a load cycle). The count is zero with a new drive. And my counter was already like >2000. That was way too much (load cycle count is one of the primary things (after reallocated sector count) that indicates a coming hardware failure (load cycling is mechanical wear)). I managed to get this under control by re-adjusting the APM setting after booting the kernel. Now the clicking noises are gone and the drive works as expected.

The point is that high load cycling count combined with an "unstable" environment (shaking, bumps, etc.) are poison for drive mechanics. I advise to try to disable APM when you want to use such a drive in the car/bus. The head's motion stabilizes it's position between the platters. I don't want to know what happens if a load cycle and a bump coincite. I'm not saying that the drive is going to die an instant death, BUT you can't hope for a long life either.

There's nowhere I can't reach.