something like the MINISAS Expander to provide

I bought some mini-sas to 4 port SATA cables today, but they didn't seem to work with the backplanes, the drives were not detected, but from a bit of research, I found that there are two types of cables, one which works with MINISAS on the host side, and SATA on the target side, and another which does SATA on the host side, and MINISAS Cable Assemblies adapters at the target side. I will search for the SATA (host) to Mini-SAS (target) cables.You can try Molex or Amphenol. These are a couple of the biggest connector and cable manufacturers. Molex is the company that came up with the MINISAS connectors and cable system. Digikey or Mouser may have cables? maybe? You are correct, most go from mini-sas host to SATA drive. You basically want pass though type cables. I do not know if Adaptec, 3ware, LSI, etc sell cables separately... but if they do, they may have 6.0 Gbps in order ones that are pass though... then again, this is not the normal configuration. A detailed forum about the HP expander is available here.I mentioned backplanes only because some have embedded expanders that allow them to accommodate more than 4 or 8 drives. You're probably not working with a system with a SAS backplane, so disregard that part and focus on expansion at the RAID card level.