> If a hard disk is intended to be used as an external USB disk or internal disk, I prefer to re-initialize it
> when it's connected as an external USB disk or internal disk respectively.
Yes, I completely agree. It is best to diagnose the hard disk in the place where it will be used.
This way we can be sure that possible problems related not only to the hard disk itself, but the whole operating environment will be detected, revealed.
For example, if the cables / connections are not perfect (and then communication issues reported), or the USB enclosure (or the PC case) does not provide enough airflow for cooling and the temperature rises.
It is better to reveal these in-place, before filling the hard disk with important data.
> I understand it's better to test and repair a hard disk in a proven environment, but "test and repair in a completely
> different environment" seems contra-intuitive. Would you please shed light on this?
Lots of things in the operating environment can cause problems. For example:
- Insufficient power or power fluctuations, over-voltages may cause spin up problems (
http://www.hdsentinel.com/hard_disk_case_spin_retry.php )
- Cables / connections can cause data communication problems (
http://www.hdsentinel.com/hard_disk_cas ... _error.php )
- The above mentioned issues or accidental removal / reset may cause weak sectors (
http://www.hdsentinel.com/hard_disk_cas ... ectors.php )
and so.
In these cases, the hard disk is not failing, just may not be able to operate correctly and can record problems, which are not really related to the hard disk, but may result in the operating environment.
This is why if a problem is reported and especially if (after fixing / stabilizing issues) problems occur again, it may be good idea to verify the hard disk in a completely different operating environment (different power source, different cables / connections and so).
For example if weak sectors or communication issues appear again and again, then the problem may be more related to the current system - and testing the hard disk drive in other system usually confirms this.