I just moved a significant amount of data from my internal backup hard drive
to an external hard drive. In the past, I have had hard drives bite the dust
and when that happened, I switched the drive from master to slave and was
able to access the data.
That's a bit odd, usually a drive does not fail then become
accessible again merely jumpering from master to slave.
Most likely situation there is that the data cable was bad
but temporarily workable again when shifted slightly during
the rejumpering, the other drive on same cable is the
problem, or you live in a very hostile enviroment (humidity
plus dust, etc) that has fouled the jumper contacts and
changing jumper settings just wipes the contact metal so it
makes a good connection again.
Does anyone know what to do if an external drive becomes inaccessable?
Take it out of the enclosure, first ready the system (enough
free space and a data recovery program installed already),
turn the system off, mount the formerly-external drive in
the system, turn system on and immediately try to copy off
the data (as soon as OS loads, don't first put more wear on
the drive by running the HDD manufacturer's diagnostics,
"yet").
If a plain copy attempt doesn't work it's time to run the
data recovery software. If that doesn't work, decide if
data is worth a large data recovery center fee, or if it's
then time to run HDD manufacturer's diagnostics and RMA the
drive to manufacturer if still under warranty.