SAS drives in Mac Pro 5,1 - HBA / PCIE question

[JDLang76]

Looking at 12gb/s SAS SSDs. OWC has a 85% sale running onMicron enterprise SSDs . 

Im considering getting 2 3.2TB models and a 12Gb/s SAS HBA and then software RAIDing them. 

I’m a little confused on speeds though... 

 

2 Questions

The Mac Pro has PCIE Gen 2. Will I benefit from a 12Gb/s HBA over a 6Gb/s HBA on PCIE Gen 2?

Can I use a 12Gb/s Gen 3 HBA in a Gen 2 slot?

 

If the SSDs only run at 6Gb/s, that totally ok. I’m in this for the capacity more than the speed. 

But if they can run at 12Gb/s speed over PCIE Gen 2, then I want to.

I’m asking because I don’t know if I should get a 12Gb/s Gen 3 HBA or a 6Gb/s Gen 2 HBA.

 

[fabafaba]

9 minutes ago, JDLang76 said:

Can I use a 12Gb/s Gen 3 HBA in a Gen 2 slot?

Yes you can, PCIE devices are backwards and forwards compatible, but it will only run at the lower speeds, 2.0 speeds in your case. If that HBA has 4 or more PCIE lanes,the connection between the SAS drive and the CPU will already be over 12Gb/s (16Gb/s, to be exact), so that doesn't matter. You shold look at the I/O speeds of the SSD though, if it can read and write at significantly more than 6Gb/s, you might as well go balls to the wall and take the 12Gb/s card to max the SSD out. If it's below 6Gb/s, there's no point in buying a more expensive HBA.