We're speccing up some 10GbE switches for integrating a few older servers into our Equallogic SAN, and we're noticing quite a price gap between SFP+ and Copper (Cat 6A) equipment (Dell 8024F vs 8024).

I'm not really sure what the real-world difference is between the form factors. The Dell guys tell me that SFP+ has a lower latency, but couldn't tell me much more than that besides that our M1000e and PS6010XV chassis's only comes with SFP+ uplinks (and SFP+ is substantially cheaper).

  • 10 years later I can say, unequivocally, the most important difference between these two standards is power consumption and thus heat generation. Jun 15, 2020 at 6:54

5 Answers 5


The latency is basically negligible. The 10GBASE-T has a latency of <1microsecond. SFP+ has less latency in itself, but SPF doesn't include some of the physical transceiver (which may or may not add latency); hence the need for a physical module (or direct copper cables).

The biggest differences are price, as you've noted, and distance. SFP+ Direct Copper the cables have to be <15m (10m for certain cables). 10GBASE-T goes the standard 100m. Cat6 cabling is quite cheap (compared to other 10G cabling), and I would suspect that the equipment manufacturers "make up for that" in the price in addition to 10GBASE-T not being as popular yet.

The 10GBASE-T standard also uses more electricity (which causes both the increased distance and latency). The extra amount used isn't normally a factor.

  • Thanks. We'll be going distances of < 3m so length definately isn't an issue. Oct 27, 2010 at 2:23
  • If distance happened to be a factor, SPF+ can also use Fiber to get much farther than 10GBASE-T anyway. I suspect that as 10G slows works into "consumer" hardware it will become substantially cheaper than SPF+; as 1000BASE-T is now compared to SPF.
    – Chris S
    Oct 27, 2010 at 2:27
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    Interesting. I wonder why Dell have chosen to go the SFP+ route then, as almost all their 10GbE equipment only has SFP+ interfaces... Could this be another VHS vs Betamax / HD-DVD vs Blueray? Oct 27, 2010 at 3:17
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    @Miles^W @skyhawk always interesting to see how our predictions come back to haunt us. I've only seen one upgrade kit (for a QNAP) that has Base-T 10GbE. Everything else is SFP+. And certainly far from standard. Nov 12, 2014 at 8:26
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    @MarkHenderson Yup. No more bold predictions from me!
    – Skyhawk
    Nov 14, 2014 at 17:35

"SFP+ has a lower latency" due the much better noise/interference isolation, but copper is generally less fragile/more durable (if it will be in a "higher chance of being re-handled" environment).

  • Given the cost of this equipment, we're hoping that it will be installed and then not touched for the next 5 years or so, so hopefully durability won't be much of an issue. Of course, we all know how these things go in real life... Oct 26, 2010 at 22:40
  • Yup... But the "much better noise/interference isolation" may come into play too depending on technology trends across its installed shelf life.
    – user48838
    Oct 27, 2010 at 1:57

The 802.3an (10GBase-T) standard calls for latency of 2.5 microseconds or better. You are dealing with storage that still has latency measured in milliseconds. The difference might matter for extremely specialized high-performance computing applications, it can't possibly have any significant impact on your SAN performance.

How does the cost difference look after you have purchased the actual cables? You may find that market prices for CAT6A patch cables are becoming almost similar to prices for CAT5e, whereas the SFP+ cabling could actually be a significant component of your project cost. (It may even cancel out the difference in switch prices.)

I would suggest that overall project cost is likely to be the most important deciding factor.

(Disclaimer: there is no 10GbE at all in my current environment.)

  • Noise/interference isolation may in some extreme/unforeseen situations or when the specifications advance forward towards tighter tolerances.
    – user48838
    Oct 27, 2010 at 2:00
  • @user48838 I don't understand (yet). Noise/interference isolation may do what?
    – Skyhawk
    Oct 27, 2010 at 2:03
  • @Miles - we've been factoring in SFP+ cables into everything as you're quite right, they're quite pricy. However once we factor in the number of switches, redundancy, NICs AND cables, SFP+ is more than $2,000 cheaper. I have no problem with SFP+, it's just not a technology I've used before, but if it's substantially cheaper and is no worse than Cat6A, then I'll go for it. Oct 27, 2010 at 2:13
  • Seems like you have a winner.
    – Skyhawk
    Oct 27, 2010 at 2:19
  • @Miles - would appear so, I was just concerned there might have been a big "gotcha" that I'm missing, but it doesn't seem to be. Oct 27, 2010 at 2:24

Here is a couple of links talking about latency with 10GBase-t. Basically 10GBASE-T is slower than 1000Base-t or gigiabit for small packets. If you are doing something like iSCSI then it will be insignificant, but if you are doing hundreds of thousands of short key/value lookups between servers that traverse several switches it can be significant and surprising that it's slower than gigabit...



Note: The latency is from 10GBase-T, not copper. If you do SFP with integrated twinax cable, that is copper but doesn't have the latency problems of 10GBase-T.


Comparing SFP+ to 10GBASE-T.

Pros of SFP+

  • Lower latency (though unless you are in HFT or similar it's likely negligable)
  • Lower power consumption
  • Cheaper NICs and switches
  • More choice of connected equipment.
  • With transcievers and fiber basically any run length can be covered.

Cons of SFP+

  • For short simplw runs needs "direct attach" cables which cost substantially more than twisted pair and are considerbally more cumbersome.
  • For longer runs or runs that need to go through patch panels needs transcivers and fiber. Fiber itself is cheap but transcievers, termination, patch panels etc for fiber an get quite spendy.

Pros of 10GBASE-T

  • Cheap twisted pair cables
  • 100m runs without messing arround with transcievers
  • Patch panels can be used without messing arround with transcievers.

Cons of 10GBASE-T

  • Higher power consumption
  • People may get tempted to use substandard cabling, just because it's twisted pair doesn't mean you can be anywhere near as sloppy as at lower speeds.
  • No good way to extend length beyond 100m (though this can be somewhat mitigated by chosing switches with mostly 10GBASe-T but also a handful of SFP+ ports)
  • limited choice of equipment.

Until/unless they can get the price and power for 10GBASE-T down it IMO has fairly limited utility.

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