I've heard conflicting information about the BPN-SAS2-846EL1

risho

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Sep 3, 2019
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Some places I've read say that this backplane will only support a single 8087 connection and expand from there, other places seem to say that it will actually support 2 8087 connections, but only if it's coming from the same hba, and others yet again seem to claim that it will support 2 8087 connections no matter what.

Does anyone know what the truth is from experience or authoritatively?

Does it support a single 8087 (4 sas2 lanes) or 2 8087 connections (8 sas2 lanes?).
 

BLinux

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This from direct experience:

1) single SFF8087 connection to 1 HBA SFF8087 port - works and shows 4x 6Gbps links.
2) dual SFF8087 connection to 1 HBA on both SFF8087 ports - works and shows 8x 6Gbps links.

I have not tried dual SFF8087 to 2 distinct HBA cards, but I would imagine that's not supported since the "EL1" means only single expander chip and I don't think it likes to talk to 2 distinct HBA controllers; but I could be wrong here... the "EL2" version is the one with 2 SAS expanders, allowing 2 distinct HBAs to connect and do multi-path to the SAS storage devices.
 
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BLinux

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which 2 ports did you connect to? or does it matter which?
if you look up the manual for the backplane, it will tell you. but basically, it is the 2 ports closest to the side edge. the 3rd one closer to the middle of the backplane should be for downstream daisy chaining to another backplane. that said, I wonder if it is possible to run 3 SAS cables and get 12 links @ 6Gbps? might be possible, i just haven't tried it...
 
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PigLover

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if you look up the manual for the backplane, it will tell you. but basically, it is the 2 ports closest to the side edge. the 3rd one closer to the middle of the backplane should be for downstream daisy chaining to another backplane. that said, I wonder if it is possible to run 3 SAS cables and get 12 links @ 6Gbps? might be possible, i just haven't tried it...
The documentation on what port is for what is only a guideline, a best practice. In reality the expander chip is basically a switch and all ports are created equal (that’s an oversimplification and a white lie - but for practical purposes it is ‘correct enough’).

The LSI expander chip supports a maximum link size of 8. So connecting a third 8087 cable to the same HBA will still get 8 lanes of throughput, not 12.

You actually can connect two different HBAs even on the EL1 expander. Generally the other HBA would be on a different host. Managing it is tricky, however. They both can’t manage the disks at the same time. Normally this would be done for an active/standby configuration with fencing to ensure only one host was active. Unless you REALLY know what you are doing this is not recommended.

The EL2 backplane actually has two separate expander chips with the second one wired to the 2nd port on dual-ported SAS drives. When using SATA drives or single-ported SAS the extra expander and it’s ports are pretty much useless and just waste power.
 

risho

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Sep 3, 2019
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I'm just happy that I'll be able to get 8 links. I just bought an 846 with this backplane $199(seemed too good to be true) and was concerned I made a mistake. I doubt that even 24 5400 rpm drives will be able to saturate 8 links. looks like my h310 will work perfectly with this thing.

thanks for the help!
 

Necrotyr

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If I use the Port closest to the edge of the board I get no link, same with the one farthest from the edge, I have to use the middle one to see my drives, this is with multiple HBAs, is my BPN defective or is there a jumper I need to set?