Previously I posted about the used 60-bay DAS units I recently acquired and racked. Since then I've figured out the basics of using them and have them up and working.
These two NDS-4600-JD-05 units each have space for 60 3.5" drives with four 6 Gbps SAS ports on each of the two controllers. The plan is to connect two R610s (eventually R620s) to each of them with the DAS units partitioned so that each of the R610s/R620s has 30 disks (well, 15-disks on each of a pair of redundant 6 Gbps SAS lines). There will be a Ceph OSD per disk on each of the 30 disks. Half of the 30 disks will be 8TB and half will be either 3TB or 2TB disks.