Any SAS Experts in the house?

My main TrueNAS box has a 12Gb SAS HBA, an LSI 9300-8i

The backplane is the Supermicro BPN-SAS3-826EL1 which is also SAS3. I have both MiniSAS cables connected from the HBA to the backplane, using all the connectors on the HBA

Soon I want to consolidate some storage and add a 2u disk shelf to this TrueNAS box so I can import my other lower performance pool from a virtualized TrueNAS setup. This is a 12 drive raidz2 consisting of all 8TB SAS disks. I do not care about the speed of this array, its literally just bulk storage.

I do have 1 spare PCI-E slot on my board where I could add another HBA for this disk shelf, but then I’m all out of slots, and I’ve increased power and heat.

Can I or should I instead drop one of the MiniSAS connectors for the backplane and throw it into an adapter to get an external connection out the back of the server for the disk shelf

Would that just limit total bandwidth for the backplane? Assuming its then limited to 48Gb/s instead of 96Gb/s, which I am fine with.

1x SAS3 lane is ~1.2GB/s . 4 lanes is 4.8GB/s … with 12 HDDs you aren’t going to write data faster than what 4 lanes of SAS3 gets you… (400MB/s per drive… that’s kind of a lot)

So yeah, drop one miniSAS from the backplane, and see if everything works fine (I don’t know how you have your array set-up, some drive names might change).

Do you know if TrueNAS cares if the drive move around? I would assume as long as the same drive is still present somewhere in the system it shouldn’t affect the pool (But, I don’t know)

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