I'll likely set it up as you and Archeon suggest. One question, how do you set the allocation unit size on a drive?

When you go to format it, it'll have some options like FAT/NTFS, Quick Format, etc. One of them should be "Default Allocation Unit Size" or similar which defaults to 2k IIRC. For a drive which has a modest number of large files (rather than a large number of smaller files) a 64k allocation unit (cluster) size will offer better performance, and no noticable loss of space. (Clusters are kept small on drives with smaller files so you don't end up wasting a 64k block for only 1k of data... Not an issue with larger files.)