10G Copper SFP+ – Necessary & Useful Option

Why is a 10G Copper SFP+ transceiver a good option to have, but can’t be recommended for mass-scale data center deployments? For more than a year, 10G Copper SFP+ transceivers have become widely available for the networking industry. Also, we see rising demand for this product, and the most popular devices currently are Cisco Nexus 3500 series and HPE FlexFabric 5930 Switch Series, where both are popular choices as ToR (Top of the Rack) switches in a data center environment. ToR switches typically focus on providing a high density of 10G/40G ports and focusing on ultra-low-latency L2/L3 data processing within a data center environment. 10G Copper SFP+ transceivers enable the use of Cat 6a/7 copper cables for 10G connectivity in data centers. Wait a minute! Legacy copper cables in modern data centers…? Why not use optical connections or Direct Attach Cables? Let’s compare these connectivity media options from the perspective of data center networking professionals who care most:

• Latency:

Latency is one of the very sensitive key indicators when it comes to data center selection. Of course, this a bit will depend on what type of applications customers will run – but starting with WEB 2.0, VMware, real-time video and audio, and ending with high-frequency trading, these all are very latency sensitive applications. So let us compare the three most popular connectivity options from a latency perspective. Typical latency for a 10GBASE-SR link based on SFP+ 850nm optical lasers and OM2/OM3 fiber is about 0.1ms. Direct Attach Cables (Twinax) typically have a latency of about 0.3ms, whereas a 10G Copper SFP+ transceiver gives a latency of 2.6ms. Such an increase in latency is because of additional line encoding overhead in the IEEE 802.3an standard, which involves doing mathematical functions on all information blocks sent over the link for error correction purposes. 2.6ms still looks quite OK, but it is OK only if you have a small number of hops. By increasing the number of 10G Copper SFP+ hops, you could easily get a serious latency impact:

Number of LinksSFP+ DACSFP+ Optical10GBase-T10.30.12.620.60.25.230.90.37.841.20.410.451.50.513.061.80.615.6

• Power Consumption:

Power consumption is the second key focus factor in data centers. Power consumption is a significant part of data center OPEX, where it is not planned to become less expensive, as energy consumption is rapidly growing and resources used to produce energy are shrinking. Data center networking professionals care quite a lot about active equipment consumption, as each watt consumed by equipment means consumption of two additional watts of cooling. So, the typical consumption of an SFP+ 850nm optical laser-equipped port is about 1W regardless of distance, a DAC Twinax cable-equipped port consumes about 1.5W in case of a typical 10m distance, but a 10G Copper SFP+ needs about 2W to 4W, depending on cable length. Again, if you have two such ports, it will not have an impact, but in the case of a high number of ports, it will eventually become significant.

• Cost:

If we compare costs, then nowadays 10G optical transceivers are mainstream in the market, and it has become very cost-efficient to use them. Also, you are no longer obligated to purchase your transceivers from equipment vendors, as we are working and focusing on saving your transceiver costs by delivering 100% functional alternatives for a fraction of the cost. Today, when this article was written, our 10G-SFP-SR module price is 16 EUR, and it is about 16 times cheaper than the price of our 10G-SFP-T module. This huge price difference is mostly because of component cost and the fact that 10G Copper SFP+ transceivers are not a mainstream choice in the market, which keeps their pricing high; in contrast, 10G-SFP-SR are among the top items in the optical transceiver industry with very affordable pricing levels.

To summarize the above ideas, we believe that 10G optical connections should be the leading choice in data centers, if compared by latency, power consumption, and cost. A 10G Copper SFP+ transceiver is a good and useful option only when you need to connect some switches, servers, or network appliances, where 10G copper is already built in. However, we would recommend limiting 10G Copper interfaces in your data center if possible and instead equipping devices with SFP+ ports.

Thank you for reading so far – this is just an opinion, if you have to add something, you’re always welcome: sales@edgeoptic.com