Yes, it looks like that's what i have to do, but it's also what i'm trying to avoid because i think i'm over complicating things. Like i said, new to Unraid, so trying to find my way around.
My tower holds 15 mechanical hdds, the goal is to end up with 12x3tb (2 parity 11 data) as main array , 1 1tb as downloader, and another 1tb as cache or "lander". If i leave this array without a cache drive the writes will be slow. So i want a separate mechanical hdd to act as cache to speed things up. I am specifically trying to avoid using the ssd for this purpose, because i will need to fill about 25 tb or so off the bat, and then this machine will remain active as i organize/delete/move new stuff over from the two old win desktops that i'm trying to retire. The point is, right off the bat i'll be putting 25tb through the 256gb ssd. I'm too lazy to do the math, but that's a lot of cycles for the ssd to go through, and is just unnecessary. A mechanical hdd would make a perfect "landing drive" for the array, which is exactly what it is when set to cache - at least that's how i understand it so far.
The problem for me then is that to keep the ssd "virgin" from all that data moving through the array i have to mount it as an unassigned device. This will complicate things a lot for configuring dockers, and is overall not advisable from what i have read so far.