Multiple disks in diskutil list

While using the terminal to create a Fusion drive I see multiple small drives in the output on diskutil list.

DIsk 3 - 15 only show up in the output when I boot into the recovery partition (⌘ R). What are these and how do I get rid of them.

MacBook Pro (17-inch Early 2011), OS X Yosemite (10.10.2)