Supermicro – Use 12 HDDs with BPN-SAS3-826EL1 Backplane

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I have got a chassis with the Supermicro BPN-SAS3-826EL1 backplane. This backplane allows 12 HDDs to be attached. However, I obviously haven't yet understood the cabling between the HBA and the backplane which I need to actually use all 12 HDD ports.

According to the first drawing on page 3-1 in the manual, PRI-J1 and PRI-J2 should be connected to the HBA (and thus are "inputs"), while PRI-J3 and PRI-J4 are "outputs" which can be connected to a cascaded backplane, which I don't have.

The manual further says that PRI-Jn are SFF-8643 connectors, which can transport the signals for 4 SAS or SATA drives. That means that I can use 8 HDDs with the backplane, although it mechanically provides 12 drive connectors.

What do I need to do to use 12 HDDs with that backplane?

Please forgive me if the question is dumb, but I have no experience with backplanes yet, and I have studied this and other Supermicro manuals several times, but still don't understand the situation.

Update / Clarification

I am very sorry that I have not been clear enough:

I'd like to use SATA drives (not SAS), and I already have a LSI 9361-8i connected to the backplane, using two cables with SFF-8643 connectors at each end. That way the controller is seeing 8 drives. Now I'd like to know how I can use the remaining 4 drives.

The board I am using has two SATA / SAS controllers integrated, each of which can handle four drives. Do I just need to connect one of them to PRI-J3 of the backplane?

Best Answer

What do I need to do to use 12 HDDs with that backplane?

You connect ONE SAS CABLE from your HBA to the backplane. DONE.

There is nothing more. THe backplane is handling the distribution of hard disc signals. SAS is like a storage network protocol and the backplane is like a switch - with every port to one HDD and the outputs for chaining for the next backplane.

Updating for the updated question:

I'd like to use SATA drives (not SAS), and I already have a LSI 9361-8i connected to the backplane, using two cables with SFF-8643 connectors at each end. That way the controller is seeing 8 drives. Now I'd like to know how I can use the remaining 4 drives.

The solution to that is to LEARN THE TECHNOLOGY. You ahve serious misconecptions. There is no two cables for SATA.

Let's start:

  • You can use SATA discs in a SAS backplane. SAS implements a SATA passthrough protocol so SATA discs show up.

  • The 2 cables are NOT for 4 discs each. RTFM. SAS is a network protocol. For uptime and more bandwidth, SAS discs support 2 uplink connections. Hence two cables. This is EVERY DISCS IS CONNECTED TO BOTH CABLES AT THE SAME TIME.

  • SATA discs are not. THey only support one uplink. So, RTFM aside which may decide to split that, IIRC, all discs connect to ONE CABLE. You can literally have hundreds of discs on one SAS link. When you use SATA, all connect to ONE of the two cables, in most backplanes that is link 1. Link 2 is not used then as NONE OF THE DISCS CONNECT TO IT.

So, the whole "4 one one, 4 on the other" is a clear sign of lacking ANY manual reading for SAS, sorry. There is no "4 discs". A SAS link is equal to 4 SATA links in bandwidth, but it still runs a combined network protocol that the backplane handles. Grab an introductory book on how SAS works. If the last 4 drives do not show up, this has NO correlation to the cabling - it is either a bad connection on the discs, a defective board, bad jumper settings somewhere OR - bad power cable connectivity. THere are a LOT of power inputs in a SAS board because of the limits of every MOLEX connector, so discs are grouped with separate power supplies provided. If everythign works as perfect, ONE cable (all that is needed) will provide connectivity for hundreds of discs. Again, this is a NETWORK protocol.

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