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We have a 3U Supermicro chassis with 16 bays on a SAS expander backplane. We have 15 of the bays occupied with hard drives at the moment. We would like to add two more drives to the backplane, but we only have 1 bay open.

Does anyone know if there is a way to “add” more SAS ports to our backplane?

EDIT: More details!

We have this motherboard which comes with an onboard SAS HBA:

inside this chassis:

I'm pretty sure this server uses the same chassis:

If you go through the configuration page for that server, you can add 16 HDs + 2 SAS SSDs. That means they're filling up all of the bays and connecting 2 SAS drives internally. The chassis comes with brackets to hold the SSDs but I don't know where they would plug into the motherboard or the backplane. The motherboard SAS connectors are both plugged into the backplane.

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check your backplane documentation. Several Supermicro models include a daisy-chain port that you can use to add more expanders.

They also sell enclosures without any motherboard, just two, three or four backplanes chained and the ports to connect to your main box. They use mostly the same components for these and 'normal' servers.

Edit: from your more details:

the chassis page, in the 'backplane' section mentions:

SAS2 Expander Backplane, features:

• Scalability through cascading

on the "optional parts" there's a "JBOD Kit - Used for cascading purposes" with some cables to pull the cascading port of the backplane to the back of the box and another to connect to another box with drives.

Also on the chassis manual there's chapter about the included backplane, a BPN-SAS2-836EL1. There you can see several configurations connecting extra backplanes on external boxes with either single or dual channels (the EL1 supports only single channels). Check C-22 and C-23 for different topologies of a single HBA driving several extra boxes.

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I'm not sure what your options for the single port are, but you can...

Add larger drives...

Add another enclosure... (SAS in/out ports, daisy-chained)

Expand the existing array...

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