Acting on information in an outdated version of the ULSAH, I have tried to wipe out my old backup disk (a USB-connected SATA drive, not an SSD) using hdparm with the following options (rather the way a toddler will go about things):
hdparm --security-set-pass foo /dev/sdb hdparm --security-erase-enhanced foo /dev/sdb hdparm --security-erase foo /dev/sdb
(I used the third command for good measure.) Later, the disk behaved in unpredictable ways.
hdparm --security-unlock foo /dev/sdb
seemed to make it possible to write a new partition table to it, and beginning a format, but that partition table did not stay. I started to get IO errors when trying to do something with the disk. Repeated attempts at unlocking the disk, or whatever, using hdparm had no further apparent effect.
As I have now realised (see http://www.tomshardware.co.uk/answers/id-1984547/secure-erase-external-usb-hard-drive.html), the whole idea seems to have been ill-advised in the first place. And having gone about this task without googling first, I don't deserve, and am not hoping for, any sympathy.
But is it possible to tell whether I have definitely bricked the external drive? Is there some kind of diagnostic tool available? It would be a pity to throw away equipment that could basically still work. (As a backup disk, it had a good life so far, with plenty of leisure time.)