From my extensive reading lots and lots about ZFS, you probably don't want all 8 disks in the same vdev. If you want to do raid-10, then start by using two disks in a mirror at install time, then you can grow your zfs pool by adding more mirror pairs to it. They'll get striped in and you'll have your RAID-10 equivalent.
My current servers I just built have two SSD's for boot/system, and 4 seagate constellations for data. I used the two SSDs on the initial install and manually created another zfs pool with the other four drives afterwards.