SuperMicro 826 Backplane Connections

[Drexlin]

tldr; What cables do I need to connect my backplane to my motherboard so that I can have 12 drives? Do I need an HBA?


Hello all,

I could use some help here. I'm new to server hardware and I'm trying to figure out what I need. So please correct me if I say something that is inaccurate. I'll only learn if I'm told

Anyway, I inherited a SuperMicro 826 server (parts list below), but there were some parts missing and, at first, it wouldn't even boot. It took me a while, but I finally found out that the power distribution board was bad, and after replacing that, I can now boot to a live USB. Yay!

Now I'm trying to figure out how to use the 12 drive bays and the backplane. I've done a lot of reading, but there are a few things that confuse me, and I'm hoping someone can clarify them for me.

The motherboard and backplane models are listed below (with links to their manuals).

According to the backplane manual, it has two SCU ports but one of them would be used in a cascaded system (which I will not need). The other would go to the SAS controller. My understanding is that this is a SAS port that is used to carry data for all 12 drives to the SAS controller.

The motherboard has a SCU port as well. However, according to the manual, it is for SATA only. So my understanding is that I can't connect my backplane directly to the motherboard. Is this correct? If so, why does my motherboard have a chip labeled "SAS CTRL"? What is this chip for?

If the SAS CTRL isn't what I think it is, then do I need an HBA that can handle 12 drives? Can that be done with one SCU port? I would imagine so, since the previous owner (which I believe was a data center) must have had it configured that way.

Sorry for the novel, please help me understand. I appreciate any advice/clarifications.

Motherboard: X9DRi-LN4F+
Backplane: BPN-SAS2-826EL1

Thanks,
Drex

 

[nthu9280]

The SCU port on X9DRi board will only support 4 SATA drives. Since you have EL1 back plane, You need a HBA (for SW raid such as ZFS etc) and one SFF-8087 cable.

Not sure where you are located but in the US,

You can get a used HBAs for under $40 such as: H240
and good quality SAS sff-8087- sff-8087 cable for < $10

 

[Drexlin]

@nthu9280 Thanks for the link! I am in the US.

Follow up question: When the description says it has 8 physical links, does that mean it only supports 8 drives? Or am I way off base here?

 

[gregsachs]

@nthu9280 Thanks for the link! I am in the US.

Follow up question: When the description says it has 8 physical links, does that mean it only supports 8 drives? Or am I way off base here?

8 drives directly connected via SFF-8087->Sata breakout cables, 4 per connector. An expander works like an ethernet switch, allowing connection of more drives.

 

[Drexlin]

Ok, I think I understand... to clarify, if I didn't have a backplane (expander), I could connect 8 physical drives using a breakout cable to the HBA. But since I do have a backplane, I allows me to connect to the HBA with one cable. Correct?

 

[i386]

Nope.
There are two kinds of backplans for storage servers: active backplanes with expanders (or pcie switches for nvme) or passive backplanes where every singe device is connected directly to the host.
Active backplanes make cabling easier, but can introduce latency and throughput bottlenecks and it is limited to the max "speed" of the used expander (or pcie switch)
Passive backplanes require a lot more cabling, but can in theory support faster standards like sas 4.0

 

[Drexlin]

Understood... but my backplane is an expander, so it will work with one cable? (By "work", I mean I can use 12 drives).

 

[itronin]

Understood... but my backplane is an expander, so it will work with one cable? (By "work", I mean I can use 12 drives).

work? Yes.
Performant? Depends.

1 SFF-8087 SAS 2 cable has an aggregate bandwidth of qty 4 SAS 2 channels @ 6.0Gbps for a total of 24.0Gbps.
If you are using SAS2 or SAS3 SSD's you might consider using an HBA with 8 channels and using 2 x SFF-8087 cables to connect.
If these are all spinners then 24.0Gbps or a single SFF-8087 cable is probably more than adequate.

 

[Drexlin]

Ah yes, understood... bandwidth is a concern. Thanks for pointing that out. Is it possible to use the second port on the backplane to connect to a second HBA port? Or am I correct in that it's only used for cascading systems?

 

[nthu9280]

EL1 - one cable for all the 12 drives. The other port is for cascading cable to connect a different chassis.

If you are planning to use mostly spinning drives, you will be more than fine.

You also have an unused port on the HBA, if you have space inside the chassis, you could technically add 4 more drives with a 8087-> 4x SATA break out cable. The MOBO you have pretty much occupies the chassis so I don’t think there will be any space.

 

[Drexlin]

Right... there's no additional room for 4 more drives.

One last question (from my original post): What is the chip on my motherboard labeled "SAS CTRL" for?

Thank you to everyone for the help!