9500-8i to 2x SFF-8087

[Brandon_K]

Does anyone have any experience in connecting a 9500-8i to a chassis with SFF-8087 ports? I realize that the a 9500 is overkill for the application, but I've picked one up for a great price in the process of ridding myself of a 9207-8i in hopes of getting better ASPM support for power reduction. One port will connect to a 12x3.5 backplane and the other to a SFF-8087 to SFF-8088 adapter, which connects to a EMC SAS shelf.

Being PCIE 4.0, this should also allow me to move the HBA to a x4 slot without bottlenecking, freeing up my x16 slot for more NVME via bifurcation.

From my research thus far it would appear that I'm after a SFF-8654 8i to 2x SFF-8087 cable? I've seen other talk of MCIO 8x cables, but I don't think this is what I'm after. I figured I would check with the pro's here before I pull the trigger on a cable.

While we're on the topic, has anyone done such an upgrade? Any issues with moving from a SAS2308 card in IT mode to a 9500?

 

[mattventura]

MCIO is indeed not what you're after. MCIO and SlimSAS (8654) are not the same. You have the correct idea (8654 8i to 2x 8087).

The 9500 is a good card, it has ASPM and is the most efficient LSI HBA from the 9300 to 9600.

 

[Brandon_K]

MCIO is indeed not what you're after. MCIO and SlimSAS (8654) are not the same. You have the correct idea (8654 8i to 2x 8087).

The 9500 is a good card, it has ASPM and is the most efficient LSI HBA from the 9300 to 9600.

Much appreciated.

I realize that with such a configuration I'm still limited to SAS2 speeds, which is fine right now. Presumably I could use a 8654 8i to 2x 8643, connect that to a SAS3 expander, then have 4+ ports of SAS3 which I can then run off to the chassis backplane and then 2 or 3 disk shelves, without any bottlenecking? If I'm doing the math correctly, the 8654 port on the 9500 gives me 8 lanes @ 12gbps each, 4 lanes per split or ~6GB/sec per split. Connecting those to a SAS3 expander would give me 12GB/sec across the entire expander and each port off of the expander (stepping down to SAS2) speeds would provide each shelf or backplane with ~3GB/sec (4 lanes, 6gbps per), effectively allowing 11 disks per shelf to operate without any bottlenecking (assuming 270MB\sec max speed for each disk).

A 9500-16i would be easier I think, but it's also nearly 5 times what I paid for the -8i.

 

[nexox]

Keep in mind when converting from SAS Gbps to GB/s that the raw link rate includes encoding overhead, in the case of SAS2/3 it takes 10 bits on the wire to transmit 8 bits of data, so 12Gbps SAS is more like 1.2GB/s data throughput (though SAS is at least full duplex.) I didn't entirely follow the math but your 4.0x4 slot will be a bottleneck before 8 lanes of 12G SAS, roughly 8GB/s (also full duplex) vs 9.6GB/s.

 

[kapone]

One port will connect to a 12x3.5 backplane and the other to a SFF-8087 to SFF-8088 adapter, which connects to a EMC SAS shelf.

If I may offer an alternative option...

Why not plug the 9500's ports into a 12gb expander first...and then cascade. SAS Expander latencies are pretty low, and unless you're running seriously low latency applications, there won't be any practical effects.

The HP 12g expanders can be had for a song...like under $20....

Pardon Our Interruption...

Plug the 9500's two ports into two ports into the expander first, and then the expander to all other expander/external chassis? You'll have more than enough ports and bandwidth to play with.

Edit: It does increase the power consumption somewhat...

 

[gaidin123]

I am doing exactly this right now and went from a 9207-8i to a 9500-8i/16i with no issues with a BPN-SAS2-216EL1 for one sff-8087 connector and the other to an external 846 jbod. ASPM works great on the card.

While shuffling some hardware around I recently put in the 16i version and am doing the multilane thing now so 2 8087 connectors go to the internal backplane and the other 2 are connected to SFF-8088 external ports. As kapone suggests you could totally stick with an 8i card and just cascade the cabling.

If you eventually decide that's bandwidth limited you could upgrade to SAS3 backplanes, or at least the primary one and just change the cabling but that's also potentially pricey.