Another thought...
DDP whilst cool, new, offering fast rebuild times and giving great multiple disk failure protection, is slower for streaming reads and random writes than RAID 6.
Dell's new Dynamic Disk pools reduces the risk of using large TB Drives - Spiceworks
Dells implemetation is also relatively untested in the real world and so hard to find others using it for comparison. I consider this a large risk factor.
Perhaps RAID 10 is a better option. It gives much better performance than RAID 5,6,DDP, and minimal rebuild times. The only downside is the very small chance of two disks in the same mirrored pair failing at the same time. This is VERY unlikely.
DDP is certainly a safer option in this respect, but you could argue that RAID 10 can deal with half the disks failing as long as they are not in the same mirrored pair!
I always think that performance is key on a VMware storage network. If I commit all my 42 2TB drives to a DDP pool and performance is lacking I am stuck. If I RAID 10 all 42 drives then I know performance will never be an issue due to RAID type (maybe just segment size or something else annoying like that!).
Thoughts?