Have a used/new install question. We are being sent a 7420 ZFS appliance, disks have been cleaned.

The zfs 7420 appliance we were shipped has clustered heads, and 5 SAS PCI cards in each controller for a total of 20 ports.  We have 14ea. DE2-24P shelves with 900 GB disks.  It also has two of these arrays with 4ea. 73GB SSD, write zilla's.  To get this configuration to work we are looking at four 3 shelf groups, and one 2 shelf group.  On the write zilla's do they have to stay in two four SSD in an array?  Or can we split them up into the groups, say 1ea. or two ea. per each of the 5