This makes sense. Would you separate archival stuff from dynamic stuff onto physical disks as well?
Yes. It makes backups easier to manage. With each unraid disk having a standalone filesystem you only have to worry about drive sized chunks of backups instead of trying to manage backing up a user share that could span many drives. Some people prefer to scatter stuff evenly across all their drives, so if they lose a couple drives only a portion of any particular share is gone. That view makes my brain itch. My user shares are confined to only as many drives as absolutely necessary to hold them. Example, disk1 has share a, b, c because they are all small shares. disk 2,3,4 only have movies, disk 5,6,7,8 only have tvshows, etc. The movies drives get filled fillup style, the tv shows are split into ongoing vs canceled so the canceled shows can be packed to the brim while ongoing shows have breathing room.