On the subject of interfacing the Brocade ICX to 2.5gbe equipment, I tried out two gadgets, both with successful results.
First is the new Qnap QSW-2104-2S, a very new product, which I purchased new from a large online retailer. This is a fanless consumer-oriented unit, with two 10Gbe SFP+ ports (there is a separate 10GBaseT version), and four 2.5Gbe RJ45 ports. I connected the Brocade to the Qnap with a DAC.
My second solution is that magic SFP+ RJ45 module, the Aquantia AQS-107-B0C2-CX. I paid a fortune for it, second hand, via ebay. This module goes directly into one of the SFP+ ports of my Brocade ICX 7250-24. The Brocade reports the link at 10G, but the RJ45 end is connected to 2.5Gbe equipment.
I did two sorts of tests on each device. First was iperf3 testing through the device under test, between a Solaris server with an Intel x520 card and a Macos laptop with a Plugable 2.5gbe USB dongle.The second test was just running speedtest.net through the device and out to the internet through my Comcast Xfinity XB7 (2.5gbe port, 1400Mbps reported throughput on a good day (maybe not even worth the effort but here we are)).
In the iperf3 testing, I was able to get performance as solid as I ever do through the Plugable dongles. I think they are the weak link. I have two of them, and in direct dongle–dongle testing between two laptops, I see mostly 2.3Gbps, but with occasional dips of a few seconds to under 1Gbps, possibly due to thermal throttling of something, I suspect the Plugable dongle or the laptop (the laptop fans spin up when I do this test -- something that does not happen on the same laptop when iperfing through my Sonnet Solo 10G interface at much higher speeds, so that is interesting in itself). I see about the same behavior between one dongle and the x520 card, passing through either the Aquantia module or the Qnap switch. If I run bidirectional iperf3, I occasionally see > 2Gbps for a few seconds, but then it decreases, and then increases (after cooling, I suppose). Unfortunately, neither of my endpoints (Macos and Solaris) show retransmits through iperf3, so I do not have that information to report.
In the speedtest.net testing, my speeds using either the Qnap switch or the Aquantia SFP+ module were on par with the speeds when I connect the Plugable dongle directly (via Cat6) to the Xfinity XB7 router.
This post is really not supposed to be a review of these other products, especially the dongle, but about how well the Qnap switch and the Aquantia module allow us to interface between our ICX switches at 10G and the 2.5gbe world. So I apologize about the limitations of my test setup, like the overheating whatevers. I hope there remains something of value.
