Buying a Supermicro 4U

[fonzie]

I want to change cases from a Norco 4224 to a Supermicro 4U 24-bay server chassis.

This is my hardware:
Motherboard: Supermicro: X9DR3-F-B
CPU: 2x Intel Xeon E5-2690 V2
Memory: 64GB Samsung PC3L-12800R DDR3 RAM
SAS Card: LSI00244 9201-16i PCI-Express 2.0

I'm looking at this case on eBay:
SuperMicro 4U Storage Array JBOD SAS2 X8DAH+-F 24xCaddy SAS2 6Gbp Expander 2xPSU | eBay

I have an assortment of drives ranging from 1TB to 6TB and I want to know if I'll run into any problems with this new case.

 

[BlueFox]

That chassis has the newer SAS2 backplane, so you'll be fine with any size drive.

 

[fonzie]

Thanks, I was definitely looking out for the SAS2 backplanes.

With this motherboard and LSI card combo, I have 6 SFF-8087 cables. I'm a little confused as to how those cables would all go plugged in to this SAS2 backplane. Most importantly, what would be the max throughput for each drive when every bay is populated?

 

[BlueFox]

Most people generally run 2 cables from the HBA to the backplane. Bandwidth is shared between the drives, so you'd be looking at 4.8GB/s total then. More than any hard drive array could do. You could run into some bandwidth limitations with a full set of SSDs, but who does such huge sequential reads/writes anyway?

 

[Stankyjawnz]

That backplane only needs one SAS connection to your HBA. I just bought that same item from ebay. It came with the SAS cable and everything (even includes an L5630).

 

[fonzie]

So I would be looking at connecting only 1 or maybe 2 SAS cables from my motherboard to the backplane and no need for the LSI card? So the total bandwidth of two 3Gbps SAS ports on the motherboard would be divided amongst the 24 drives? So if I estimate 6Gbps divided by 24 drives would be 31MB/s (and that's not accounting for the overhead)? This seems way off. Someone please help me understand how two 3Gbps SAS cables can provide enough throughput to max out 24 drives read speeds.

*I run unRAID and the monthly parity checks require reading from all drives simultaneously

would an 846A backplane suit my needs better since it has 6 SAS inputs and I assume allows for more bandwidth?

edit: I just re-read your post and noticed it was GB/s not Gbps. Can you please explain how you came about that number? thanks.

 

[BlueFox]

Each SFF-8087 port is 4 lanes, not 1. You'd have 2.4GB/s at 3gbit and 4.8GB/s at 6gbit with 2 cables. Plenty for hard drives. No need to get the A-type backplane unless you're using primarily SSDs.

 

[fonzie]

I have two SAS (SFF-8087) ports on my motherboard rated at 3gbps each. So could I use the motherboard ports instead of the card and keep those same 4.8GB/s speeds?

Also, the LSI card I have has 6gbps SAS ports. Does that mean I would potentially have 9.6 GB/s if I connected two of those ports of my HBA to the SAS2 backplane on the Supermicro?

 

[BlueFox]

No, you'd be getting 2.4GB/s out of the motherboard and 4.8GB/s out of the HBA with 2 cables.

 

[fonzie]

Why is there a difference between 2 onboard SAS connectors versus 2 HBA SAS connectors? Do the motherboard SAS have fewer lanes?

 

[BlueFox]

No, same number of lanes. You just said the motherboard was 3gbit and the HBA was 6gbit, so the HBA will be double the speed of course.

 

[fonzie]

Okay, I just re-read your previous post and it made sense to me. So if I were to connect the two onboard SAS 3gbps connectors, I would have 2.4GB/s total to divide among the 24 drives, which would be about 200MB/s? I think that answered my question. Thanks for the clarification

 

[BlueFox]

Almost. 2.4GB/s divided by 24 would be 100MB/s each. Still plenty for hard drives to be honest. Keep in mind that that doesn't mean that none of the drives can exceed 100MB/s. If you're not utilizing all of them concurrently, you would get higher speeds on each drive.

 

[fonzie]

Wow, can't believe I made that simple math error. Haha, thanks for correcting me.