[OT] Life expectancy of powered down hard drives....

[Norberto Meijome]

hi all,
I know this doesn't relate to FBSD per se, but I figured i'd try to pick 
your brains :)

I read somewhere (sorry, cant remember where) that hard drives fail if 
not powered up every so often (not sure of time frames, but the 
discussion was about tapes still being better for backups than hard 
drives if planning for long term storage). It was also mentioned a 
"knock on the centre of the drive" to bring it back to life (??).

How much truth is in this? I have EIDE drives that I havent used in 
years and I just tested them and they work fine...but again, I've had an 
instance of a new drive, used twice to backup some info and then left 
untouched for 10 months, and it wouldn't even spin up...

Does this affect SCSI drives? I suppose it would be more likely to 
affect desktop-quality IDE / SATA drives...

Any insights will be much appreciated.

Best regards,
Beto