If you have a laptop with a hard drive in it, make sure you give it a chance to park the drive before you pick it up.
A Little Bit about How Hard Drives Work
Inside the case, hard drives look kind of like old school record players, with a head that hovers over the platter for reading and writing. The head never touches the hard drive–data is stored and retrieved magnetically. The distance between the head and the platter is tiny but crucial.
When you suddenly move your computer it’s possible to send the read/write head slamming down onto the platter, or skittering across the surface. Either of these can cause you to lose some or all of the data that’s stored on the disk.
Most laptops these days have sudden motion sensors to try to protect your hard drive in case of a fall. These systems will automatically park the hard drive head off the platter when a drop is detected. While this will protect you in most cases, it’s not prudent to use it as a replacement for proper care.
Solid State Drives are Different
Some new computers, including MacBook Airs, come with a new type of storage called a “Solid State Drive,” or “SSD.” SSD’s don’t have the moving parts that traditional hard drives do, so head crashes are not an issue.
Safely Moving your Mac
When you set your computer to “sleep” on a Mac–either explicitly through the menu or implicitly by closing the lid–it saves the current state of memory by writing it to disk, parks the hard drive head safely off the platter, and then enters a power saving mode. This means that immediately after you indicate that it should sleep, the hard drive head is moving around to write data to disk–which is exactly when you should not move your computer.
When the process is complete and the hard drive head is parked, the power light on the Mac gently pulses to indicate that it’s safe to move. Always wait for the light to pulse before you pick the computer up and move with it.
Safely Moving your PC
“Hibernate” on a PC is like “sleep” on a Mac: memory is written to disk and the hard drive is parked. As with a Mac, in the seconds after you choose “Hibernate” the hard drive is writing data to the drive and the computer should not be moved.
“Sleep” (or “Standby”) on a PC is a little different–it doesn’t write the contents of memory to disk, and instead immediately parks the hard drive head and goes into a low power state.
When you put your PC to sleep, wait at least five seconds for the hard drive to park itself. If you’re entering hibernation mode, you should wait for it to stop writing to the hard drive, by either listening to the hard drive or watching the disk access light–and then wait a few seconds more.