Windows Server 2012R2, with three 8-drive JBOD, NO EXPANDERS, each of three 8-drive JBODs fans out eight primary sata 7-pin connectors and eight secondary sata 7-pin connectors. Sometimes a JBOD of SAS drives with primary and secondary sata 7-pin connectors is called "dual domain". Server 2012R2 has MPIO or multi-path IO. I think this means that access to a single drive can be through the TWO 7-pin connectors. Correct me if I'm wrong. The system has all 24 drives as "Direct Attach" so again, no expanders. 24 drives X 2 connectors per drive is 48 connectors which is 48 SAS ports. Since no expanders, I need 48 ports of host bus adapter. I did a great amount of calculation on how much a PCIe 3.0 8-lane bus connector can take before it reaches saturation. I can put up this excel sheet if anyone wants it. I have four Adaptec 81605ZQ, each with 16 NATIVE ports, so that's my 48 ports (16X4-48). All primary ports of all drives go to Adaptec 0 and 1. All secondary ports of all drives go to Adaptec 2 and 3. I can put up a system diagram if anyone wants it. The three 8-drive JDODs are arranged as a three way mirror. The drives are 4 TB each. So my capacity is 1/3 of the 24 drives or 1/3 X 24 X 4 = 32TB. Server 2012R2 allows drives to be set up in so called columns. Am just starting to address this, so no comment yet. MS says a three-way mirror will increase read speed significantly. I have added two Seagate 1200 SSDs and will be testing Storage Spaces and Storage Pools Tiering. This is a research project needing extremely fast access to blocks of data in a set of drives and nearly instantaneously must read out a block of data. We tried all ways of using SATA drives without dual-domain dual ports and can't get the input output rates we need. So were trying two port sas drives which also have ability to read and write nearly at same time.