Tuesday, July 27, 2010

Cost Effective 10G Data Center Networks

by Lisa Huff

For networks running Gigabit Ethernet, it’s a no-brainer to use Category 5e or 6 cabling with low-cost copper switches for less than 100m connections because they are very reliable and cost about 40-percent less per port than short-wavelength optical ones. But for 10G, there are other factors to consider.

While 10GBASE-T ports are now supposedly available on switches (at least the top Ethernet switch vendors, Brocade, Cisco and Extreme Networks say they have them), is it really more cost effective to use these instead of 10GBASE-SR, 10GBASE-CX4 or 10GBASE-CR (SFP+ direct attach copper)? Well, again, it depends on what your network looks like and how well your data center electrical power and cooling structures are designed.

First, 10GBASE-CX4 is really a legacy product and is only available on a limited number of switches so you may want to rule this out right away. If you’re looking for higher density, but you can’t support too many higher power devices, I would opt for 10GBASE-SR because it has the lowest power consumption – usually less than 1W/port. And also, the useful life of LOMF is longer; it’s smaller so won’t take up as much space or block cooling airflow if installed under a raised floor.

If you don’t have a power or density problem and can make do with just a few 10G ports for a short distance, you may choose to use 10GBASE-CR (about $615/port). But, if you don’t have a power or density issue and you need to go longer than about 10m, you’ll still need to use 10GBASE-SR and if you need a reach of more than 300m you’ll need to either install OM4 cable (which will get you up to 600m in some cases) to use with your SR devices; or look at 10GBASE-LR modules ($2500/port) that will cost you about twice as much as the SR transceivers (about $1300/port). If your reach needs to be less than 100m and you can afford higher power, but you need the density, 10GBASE-T (<$500/port) may be your solution. If you have a mix of these requirements, you may want to make sure you opt for an SFP-based switch so you can mix long and short reaches and copper and fiber modules/cables for maximum flexibility.

So what’s the bottom line? Do an assessment of your needs in your data center (and the rest of your network for that matter) and plan them out in order to maximize the cost effectiveness of your 10G networks. One more thing – if you can wait a few months, you may want to consider delaying implementation of 10G until later this year when most of the 10GBASE-T chip manufacturers promise to have less than 2.5W devices commercially available, which will drastically reduce (about half) its per port power consumption.

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