27 Apr 10G Copper SFP+ – Necessary & Useful Option
Why 10G Copper SFP+ transceiver is good option to have, but can’t be recommended for mass scale data center deployments? Already more than year 10G Copper SFP+ transceivers have become widely available for networking industry. Also we see raising demand for this product and most popular devices currently are Cisco Nexus 3500 series and HPE FlexFabric 5930 Switch Series, where both are popular choice as ToR (Top of the Rack) switches in data center environment. ToR switches typically focus on providing high-density of 10G/40G ports and focusing on ultra-low-latency L2/L3 data processing within data center environment. 10G Copper SFP+ transceiver are enabling ability to use Cat 6a/7 copper cables for 10G connectivity in data centers. Wait a minute! Legacy copper cables in modern data centers…? Why not to use optical connections or Direct Attach Cables? Let’s compare these connectivity media options from perspective we think data center networking professionals would care most:
Latency is one of very sensitive key indicators when it comes to data center selection. Of course, this a bit will depend 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 three most popular connectivity options from latency perspective. Typical latency for 10GBASE-SR link based on SFP+ 850nm optical lasers and OM2/OM3 fiber is about 0.1ms. Direct Attach Cables (Twinax) typical latency is about 0.3ms, whereas 10G Copper SFP+ transceiver gives latency of 2.6ms. Such increase in latency is because of additional line encoding overhead in IEEE 802.3an standard, with doing mathematical functions on all information blocks sent over link for error correction purposes. 2.6ms still looks quite OK, but it is OK only if You have small number of hops. By increasing number of 10G Copper SFP+ hops You could easily get serious latency impact:
|Number of Links||SFP+ DAC||SFP+ Optical||10GBase-T|
Power consumption is second key focus factor in data centers. Power consumption is 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 typical consumption of SFP+ 850nm optical laser equipped port is about 1W regardless of distance, DAC Twinax cable equipped port consumes about 1.5W in case of typical 10m distance, but 10G Copper SFP+ needs about 2W to 4W, depending on cable length. Again – if You have two such ports it will not play an impact a lot, but in case of high number of ports it will become significant eventually.
If we compare costs, then nowadays 10G optical transceivers are mainstream in the market and it has became very cost efficient to use them. Also You are not any 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 fraction of the costs. Today, when this article was written, our 10G-SFP-SR module price is 16 EUR, and it is about 16 times cheaper, than price of our 10G-SFP-T module. This huge difference in price is mostly because of component cost and fact that 10G Copper SFP+ transceivers are not mainstream choice in the market, which keeps their pricing high, as opposite 10G-SFP-SR are among top items in optical transceiver industry with very affordable pricing levels.
To summarize above ideas, we believe that 10G optical connections should be leading choice in data centers, if compared by latency, power consumption and cost. 10G Copper SFP+ transceiver is 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 to limit 10G Copper interfaces in your data center if possible and instead equip devices with SFP+ ports.
Thank You for reading so far – this is just an opinion, if You have to add something – Your’re always welcome: [email protected]