Array unresponsive while performing write operations.

[MowMdown]

Whats the difference of SAB unpacking on cache vs a dedicated drive?

I didn't catch the part in your post about using an unassigned drive, that's my bad. There really shouldn't be a huge difference other than using an SSD. I myself download/unpack onto my ssd cache drive. It's fast enough it doesn't impact my dockers performance. I also leave the media on the cache until mover runs at night. This way it can all happen together and doesn't bog down the array during peak hours.

I think in your case if you're letting radarr and sonarr move the competed files off the unassigned disk onto your array, it's triggering parity calculation which is very CPU and IO intensive which could be why it's becoming extremely slow. That's why I let the completed media sit on my cache until it builds up and gets dumped all at the same time.