Hi everyone, I asked the question yesterday but I probably didn't provide enough information for a reasonable response. So here it goes.
I have a NetApp 4246 and I'm looking to get an HBA and some cables to connect everything up.
I don't understand how the maths works with these disk shelves. Each drive can do a max of 2Gbps. The disk shelf can house 24 drives, so that's 48Gbps. Each SAS cable supports 4 SAS lanes @ 750MB/s, that's 3GB/s and 24Gbps. So my maths suggests you need one cable per 12 drives. So a standard 2 port HBA card should use both ports going to the disk shelf.
Everywhere it says that you just need one cable to connect the HBA to a single IOM unit. The documentation on page 46 shows a single-path, single-controller scenario where they have multiple disk shelves daisy chained from ONE cable.
How does that work!? It seems like you're getting half the performance with just a single disk shelf, let alone daisy chaining.