What are the dangers of leaving my external USB drive mounted?

[jc at trillian.mit.edu (John Chambers)]

David Kramer writes:
| I have an external USB drive that I back up to.  Right now, I turn it on,
| mount it, back up, unmount it, then power it down.  This is to minimize
| the likelihood of anything happening to my server also taking down my
| backup drive.
|
| I am contemplating either leaving the drive on and just mounting it when I
| need it, or leaving it mounted.  Both computer and drive are on a UPS.
| What would the added danger be if I leave the drive mounted?  I'ts ext2,
| IIRC.

One danger is a lightning strike on  your  wiring,  which  could  fry
anything  plugged  into  your computer.  The only sure way to protect
from this it have no electrical connection to the backup medium. Then
you computer may be fried, but your backup data will be safe.

This  is  more of a danger in summer, of course, and if you're near a
hilltop (as we are), it's  more  likely.   I've  never  actually  had
lightning  strike  our house, though I do worry whenever a good storm
passes through.