The downtime for March 5th is cancelled.  The drive in question has only a single failed sector.  SMART estimates more than six years of life remaining.  It would not automatically re-allocate the failed sector on a read, apparently it can only do this on a write which is odd since it’s part of a RAID array it could have gotten the data from the mirror drive.  Oh well, instead of physically replacing it, I’m going to fail it (stop the RAID from using it, overwrite that sector to force a re-allocation, then restore it to service which will cause the raid software to mirror it from the operational drive.  All this can be done without interrupting service.