The speed with expander vs without expander

[Hyunseok_Kim]

I am wondering If I can increase the read and write speed of TrueNAS.

Currently, my twenty-four 12G SAS HDDs are mounted on the 12G SAS backplane with an expander chip and connected via Broadcom 9500-16i HBA card. so the maximum speed is around 24Gbit/s.

If I switch the backplane with the expander chip to the backplane without the expander chip and mount my SAS 12G HDDs directly with HBA cards (add one more same Broadcom 9500-16i HBA card), can I increase the read and write speed?

Thank you in advance.

 

[ChrisRJ]

How would we know? Seriously, you need to provide a lot more information, esp. about pool/vdev configuration. What is you current speed, how did you measure it? How does your workload look like?

 

[Ericloewe]

24 HDDs, at full tilt, might optimistically manage to push 36 Gb/s total. A SAS3 expander, even with just four lanes connected upstream instead of eight, has 48 Gb/s of bandwidth in each direction.

You could do this, but it's akin to throwing money into a fire pit. Very mildly interesting experience, I expect, but a very costly one. Plus you'd likely burn more power, waste PCIe connectivity, etc.