Connecting Backplane properly at Supermicro 846BE1C-R1K28B

[mifronte]

I am just starting to understand SAS backplane and HBA. I am a little confused when you have 24 drives connected to only 8 SAS lanes, wouldn't there be a bottleneck if you had to access all 24 drives at once?

Since 8 * 12Gbps = 96Gbps total bandwidth. With 24 SATA3 (24 * 6Gbps) you would need 144Gbps total bandwidth. More if you use SSD SAS drives.

Wouldn't the ideal scenario for a 24 drive chassis is to have at least a backplane with 6 SAS ports giving you 24 SAS lanes? Or is this the case where no mechanical drive can achieve the 6Gbps rate.

 

[Ericloewe]

HDDs barely saturate SATA 1.5Gb/s, as you guessed.

Besides, 96Gb/s is more than just about anything that your server can handle moving around.

 

[Stux]

And the PCIe lanes are bottlenecks. The sas2 cards are limited to 32gbps and the sas3 to 64gbps

 

[danb35]

if you had to access all 24 drives at once?

...and how often do you think that will happen?