This screen informs you that some tiers need to be converted to Dual Redundancy. Click Modify Storage Type to go to the next screen.
Disks larger than 2.6 TB require Dual Redundancy storage.
Dual Redundancy for large disks protects against data loss during the long rebuild process required if large disks fail.
Converting to Dual Redundancy will likely cause a RAID Rebalance operation.