Not sure how this relates, but after I copied the SM archive folder to a folder on a new drive, I changed the path setting in SM, stopped the SM Windows service, made sure that the archive files in the new location were fully up-to-date, and then restarted the SM service. It went very smoothly (did this at night), and it only took a couple of minutes to complete. A short time later, I deleted the original (now inactive) archive folder.