Okay, the spuds and the drives work like a charm:

[root@ultralord ~]> format
Searching for disks...done


AVAILABLE DISK SELECTIONS:
       0. c0t1d0 <DEFAULT cyl 30391 alt 2 hd 255 sec 63>
          /pci@0,0/pci108e,5351@1f,2/disk@1,0
       1. c0t3d0 <DEFAULT cyl 38910 alt 2 hd 255 sec 126>
          /pci@0,0/pci108e,5351@1f,2/disk@3,0
       2. c0t4d0 <DEFAULT cyl 38910 alt 2 hd 255 sec 126>
          /pci@0,0/pci108e,5351@1f,2/disk@4,0
Specify disk (enter its number): ^D

I want to create a pool for building kernels:

[root@ultralord ~]> zpool create builds c0t3d0 c0t4d0
[root@ultralord ~]> df -h /builds
Filesystem             size   used  avail capacity  Mounted on
builds                 1.1T    19K   1.1T     1%    /builds

Hmm, while I like the space, these are 640G HDs. Wait, I didn't use raidz:

[root@ultralord ~]> zpool  destroy builds
[root@ultralord ~]> zpool create builds raidz c0t3d0 c0t4d0
[root@ultralord ~]> df -h /builds
Filesystem             size   used  avail capacity  Mounted on
builds                 587G    19K   587G     1%    /builds

Much better - now I need to get some source and let it rip!