I just wanted to share my experience with this HBA when it comes to U.2/U.3 drives, because it was quite frustating and cost me a lot of money:
I have no idea how a backplane would fit into this and whether or not it would have similar problems.
- U.2/U.3 drives normally register as /dev/nvme[0-9]+n[0-9]+ where the n[0-9]+ represents the namespace number. The Broadcom Tri-Mode controller however only supports the drives as SCSI devices, meaning they will show up as /dev/sd[a-z]. As a consequence, you have NO support for any kind of nvme functions, like creating namespaces, changing the namespace lba format size, etc.
- The Broadcom cable 05-60006-00 (x8 8654 to 8xU.3 Direct, 1 meter) suggests that you can attach 8 U.3 drives (not U.2, as U.3 drives can be plugged into U.2 ports, but not vice versa!) to one of the SlimSAS SFF-8654 8i outputs (the 9500-8i only has one of those). However, it does not use the PCIe 4.0 x8 lanes with which the card is attached to the motherboard in a switch chip way, but rather "splits" them, meaning that with this cable each of the 8 U.3 drives would only get one x1 PCIe lane, which is NOT SUFFICIENT for some U.3 drives, like my Micron 7400 Pro. The U.3 drive is not recognized, it just doesn't show up.
There are a few additional requirements for it to function. From the manual:
Enables direct connect from the adapter to a U.3 NVMe or SAS/SATA drive. This cable does not send
a PCIe REFCLK or PERST# to each drive connector; that is, the U.3 drive must support SRIS and not
require PERST#. Use for proof-of-concept type applications.
- Only the Broadcom cable 05-60005-00 (x8 8654 to 2xU.2 Direct, 1 meter) allowed me to connect two Micron 7400 Pro to the adapter. This effectively limits the 9500-8i to two U.2/U.3 drives, no more. Considering it is using x8 lanes to the motherboard, you'd be better off with a bifurcation PCIe 8x to 2x U.2/U.3 card. It costs far less than the Broadcom HBA and gives you full access to the nvme controls of the drives.
I have no idea how a backplane would fit into this and whether or not it would have similar problems.