Best span size for 12 x 2TB drives in RAID10

We have just taken delivery of a new JBOD chassis, with 14 x 2TB NL-SAS drives - 2 have already been earmarked for enclosure spares, so we have 12 drives available.

I have several options for setting up the RAID10 array (unfortunately the head unit won't allow odd-numbered spans):

• 6 x 2-disk spans (12TB raw)
• 3 x 4-disk spans (6TB raw)
• 2 x 6-disk spans (4TB raw)

I would like to get the most usable space so 6x2 is looking favourable and 2x6 doesn't give anywhere near enough space, but I'm wondering if there's any performance or risk hit with going with 6x2 over 3x4.

I think that 6x2 is more risky because each span can only lose one drive - but are the two hot-spares enough to mitigate this?

Can someone sanity-check my reasoning or give me any pointers?

Head unit is an FC Infortrend ES-DS 3024 SAN, and workload will be Veeam backup storage if it makes any difference.