I’m in the process of building up a Supermicro SC847 case with X10 motherboard. The case includes the 2x2.5" drivekit and has BPN-SAS3-846EL1 and BPN-SAS3-826EL1 backplanes that are connected with two cables from the HBA and cascaded to the second backplane with another 2 SAS cables.
Wondering if I am able to connect this 2x2.5" drivekit via another SAS cable off of a third connector on say a 9305-16i or 9400-16i. The drivekit also has an SGPIO header which would connect to the motherboard SGPIO header when connecting to a motherboard SATA connector. Do I need to connect the SGPIO to anything if using SAS? Would like to get this drivekit connected via SAS if possible and am trying to avoid the onboard SAS controller.
You definitely can. I wouldn’t recommend it for the typical use case of booting from those disks, but it does work. So much so that I had a server (SC826, but same concept) delivered to me at work in 2020 wired up like that, much to my chagrin - but it did work without any issues. It’s actually even weirder, because I ordered it with an SFF-8643/SFF-8644 adapter to plug in an external disk chassis - so they wired one the of those ports directly to the HBA and the other is hanging off of the expander backplane, along with the rear 2.5" bays.
On the host side of an SFF-8643 (or SFF-8087) breakout cable, the SGPIO stuff is built-in. The drive cage side has a pin header, IIRC.
I expect that 95% of users just do a mirror of boot SSDs in there, and for that simpler is better, which means PCH SATA ports. The only benefit of SAS would be for better performance, with 12 Gb/s SAS SSDs, but that’s pointless for the OS and strictly worse than NVMe, using the other kit Supermicro sells, which occupies the same spot in the chassis.
I don’t feel the need to mirror boot drives as this is in my home lab which I can easily walk up to if I have an issue. Boot speed is not important to me, so I have started on path to put a SAS HDD in there for OS, swap, etc. and an SSD as mentioned for the L2ARC and ZIL.
So it sounds like this weird setup would work from what you are saying. Supermicro told me not to cascade off of the second backplane to connect these drives because of “resets”. So exploring if I can directly connect these to the HBA instead.
