Replacing failed mirrored USB Boot device; hopefully simple question

[RonRN18]

Today, I had one of my two mirrored USB boot devices fail. It reports as degraded with a critical alert. I have purchased another identical device and wanting to know the process. First, I do not know which device it is, I only know it isn't da8p2, which is the good one. Can I pull one of the two out of a running system without a problem to see if my first random guess is correct? Do I need to "detach" the failed drive from the GUI first? Do I hit "Replace" when I have pulled out the bad drive and ready for it to "resilver"?

 

[dlavigne]

A quicker method is to save your config, do a fresh install of the same version to the two good sticks, and restore your config.

 

[RonRN18]

A quicker method is to save your config, do a fresh install of the same version to the two good sticks, and restore your config.

It appears I will have to do that, as all other options have failed. The "Replace" does not work, neither does "Detach" for the failed one.