I have SABNZB installed on the the cache disk. Downloads are initially downloaded and unpacked to the cache disk. Is there when this happens also access to the parity because data is written to the cache disk? My understanding is that the cache is not an arraydisk, so this shouldn't happen.

I have SABNZB installed on the the cache disk. Downloads are initially downloaded and unpacked to the cache disk. Is there when this happens also access to the parity because data is written to the cache disk? My understanding is that the cache is not an arraydisk, so this shouldn't happen.

True, the parity disk is not read or written when the cache drive is written.  It MAY spin up if in the same spin-up-group as a data group, but that has nothing to do with reading or writing.