AUGUST 2019 MACWORLD 117replacement
adapter if it thinks
that’s the problem.
- The drive’s
case is going bad
This is another
hard thing to
diagnose separate
from the drive. A
drive has its own
operating system,
circuit boards, and
chips, but a case
also has
components, firmware, and a power
supply (unless it’s powered via the USB or
Thunderbolt 3 bus). If you think the drive is
fine and the case is a problem, you may
be able to swap the drive into another
case to test. Cases for 2.5-inch (mobile)
and 3.5-inch (desktop) drives can be very
inexpensive—as little as $10 to $20. - The drive is failing
Often, there are signs ahead of time that
something’s going wrong, and modern
drives record diagnostic problems to an
internal log. Unfortunately, Apple doesn’t
have a tool that provides easy and direct
access or evaluation. I recenlty posted a
review (go.macworld.com/drev) of DriveDx
from Binary Fruit (go.macworld.com/drve),
and it helped me diagnose not one, but
two external drive failures in time to rescue
data. One of the drives had corrupted files
and macOS would freeze when trying to
access those. But the other, seemingly a
little better off, began to unmount itself
suddenly. I had to replace both.- The computer’s peripheral bus
is failing
While this seems unlikely, you can read
about how I discovered this problem with
a Mac mini a few years ago (go.macworld.
com/evry), which led to enormous
amounts of wasted time and massive
data-recovery efforts.
My best advice? Don’t put off
troubleshooting mysterious unmountings,
because either something’s already wrong
or about to get worse.
DriveDX helped me diagnose external drive failures.