On my EX2 Ultra, I have the disks as separate volumes and I had a Time Machine share on each, and I could back up to each, alternately.
After “upgrading” to OS5, I can no longer do that. Time Machine can only access one share, tthe last that has been designated and updated using the admin portal.
Has this happened to anyone else? I wanted two backups in case one drive failed but looks like I might have to re-RAID the device and reset to factory config to get that feature. I was using the rest of each disk to store media.