I'm not able to "Create Storage"

I don’t see the “Start” button here, even though I have my disks connected to my server. My dashboard can find and recognize those devices and are shown as separate “USB” drives. My Google searching tells me that Zima doesn’t allow RAID setups with USB drives, but I was following along to Dammit Jeff’s video “I Spent a Year Replacing My Subscriptions. Here’s How.”, which includes a clip at 19:28 that already has the “Start” button. In that same video, he also uses the same USB DAS setup that I’m using, so I’m not sure what I’m doing wrong or misunderstanding.