The RAID array is having its drive replaced. However, the replacement drive is getting its checksum integrity set up, which will take a few hours. So for now, the array (which holds the entire website data, barring config files) is mounted in a degraded state.

I do have the old 2TB drive; will zero that one at some point. If the pending sectors do not remap, this will be used for another purpose rather than going back in the array. Amusingly, worse-faring drives are added to the Jellyfin and Live TV servers due to being very cheap.