Possible front-end port oversubscription on Dell PowerStores

While architecting an environment with a Dell PowerStore for a customer, I noticed some interesting details in the “Dell PowerStore: Best Practices Guide”

First a part about the on-board mezzanine card:

This means the ports on the mezzanine card have about 63.04 Gbits/sec of bandwidth available. When using 4 ports at 25Gbit/sec, we can not use the full bandwidth these ports offer. So what about the I/O module slots?

This part is about the I/O module slots? Slot 0 is 16-lane PCIe Gen3 which gives you about 126 Gbit/sec, which should be sufficient for the 4 port 25Gbit/sec card …

But ….. Regarding the I/O module:

So the 4 x 25Gbit/sec I/O module itself is 8-lane PCIe Gen3 …. So even in slot 0 you can not use the full bandwidth of this card ….

Since PowerStore OS there is a new 2-Port Ethernet card that supports speeds of up to 100 Gb/s. This 100 GbE card is supported on PowerStore 1000-9200 models in I/O Module 0 slot, the 16-lane PCIe Gen3 slot, which is still limited to 126 Gbit/sec ….

If you want to combine ethernet connectivity and Fibre Channel, it gets even more interesting, since the preferred slot for the 4 port 32Gbit/sec FC I/O module is slot 0 …. In slot 0 it can run at full capacity. When adding more FC ports to slot 1, the combined ports bandwidth is again limited to 63.04 Gbits/sec

So when designing a high bandwidth PowerStore environment, keep this in the back of your mind ….

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