The Data Center Buying Guide for DAC Cables

You’re (very) interested in the potential cost savings of Direct Attach Copper (DAC) cables. With a low price point, DACs just may be the perfect intra-rack solution for your data center. 

How do you decide which DAC is best? And, if it works for your application?  To give you a leg up, answer the essential questions below to help you decide if a DAC, and which DAC, is the right solution. 

Questions to ask when selecting DAC cables and DAC breakout cables

  1. Is low latency important?
    If yes, them DACs and breakout DACs both provide very low latency.
  2. Am I looking for ways to reduce heat in my facility?
    If yes, then DACs and breakout DACs generate almost no heat.
  3. Am I concerned about power consumption and/or high utility costs?
    If yes, as DACs and breakout DACs generate almost no heat, there’s less to cool. And DACs and breakout DACs do not require electricity. (Exception: active DACs contain electrical components for signal boosting over distances up to 30m).
  4. Is cable length a determinant?
    If less than 5m, select passive DACs and breakout DACs. For lengths from 5m to 15m, use active DACs and active breakout DACs.
  5. Is speed critical to our operation?
    If yes, DACs and breakout DACs support speeds up to 400G.
  6. Do I need multi-vendor compatibility?
    If yes, maybe DAC. This is dependent upon the manufacturer of your switches, servers, routers, and so on. See the manufacturer’s specifications.
  7. Do I have concerns about dust and robustness?
    If yes, DACs may be an option due to their sealed manufacturing and low parts or components.
  8. Am I upgrading my intra-rack switches from 25G to 100G, 200G, or 400G and connecting to the same servers?
    If yes, then DAC breakout cables in x2, x4, or x8 would work depending on your rack setup.
  9. Is port density of newer, high-speed switches a concern?
    If yes, DAC breakout switches will allow you to connect a single switch port to up to 8 switches depending on their speed (25G, 50G, 100G, 200G).
  10. To keep my costs balanced or to fulfill a rolling budget, can I replace existing AOCs with DACs in batches instead of all at once?
    Of course! DACs can be replaced in an entire facility to maximize savings and improve latency. Or one at a time.
  11. As I plan to expand my facility, will I save money using DACs instead of AOCs?
    The initial purchase price of DACs is 50-80% less than AOCs. And, that does not include the lifetime energy savings from zero consumption and zero need to cool.
  12. As I upgrade my switches, can I replace AOCs with either DACs or breakout DACs?
    Yes. As switches move to higher speeds up to 400G, select the DAC breakout cable that matches the switch and your existing servers.
  13. Can I count on DACs—copper cable—for performance and reliability?
    Yes. Under test conditions, DAC performance was superior to AOCs.
  14. How do I know if I need passive or active DACs?
    Some network switches require electrical components in the connectors to boost the signal over a longer distance (aka AEC). See the manufacturer’s specifications.
  15. Are DAC cables and breakout DAC cables interchangeable by manufacturer?
    Technically yes. We recommend that you purchase from reputable companies that stand behind their products and validate quality. Standardization on a product that is unavailable due to supply chain issues, bumped orders due to priority, or poor responsiveness should be avoided if 100% uptime is the goal.
  16. Do I need to be concerned about AWG (American Wire Gauge)?
    AWG is simply an identification of the cable diameter. DAC cables are available in  24AWG, 28AWG and 30AWG where the lower AWG value (paradoxically) is thicker and less bendable than a higher AWG. That means that higher data rate DACs (400G) are thicker than lower data rate DACs (100G).
  17. How do I choose the right connector?
    Below is a general guide to common connectors for your network’s requirements.
SpeedDirect Attach Copper CablesDirect Attach Copper
Breakout Cables
40GQSFP+QSFP+ to 4x 10G SFP+
100GQSFP28QSFP28 to 4x 25G SFP28
200GQSFP56QSFP56 to 4x 50G SFP56
200GQSFP-DDQSFP-DD to 2x 100G QSFP28
400GQSFP-DDQSFP-DD to 4x 100G QSFP56

Need help or assurance that you’ve picked the right DAC?

We believe you have two options:

  1. Save yourself some time and contact Vitex. One of our experienced application engineers will analyze your application and concerns and recommend the perfect part. You can even test a sample at no charge just to make sure it works. And convince your boss and purchasing department to make the investment.
  2. Answer all these questions. And then contact Vitex. We’ll confirm your conclusion and order a test product if you’d like one.

No matter your selection process for a direct attach copper cable, get ready for low latency, lots of savings and reliable performance.


If you’re in need of guidance, just ask. For most of our data center and network clients, the selection and standardization of cables is a skill they rely on Vitex application engineers for.

To learn more about DACs, we recommend:

We invite you to talk to an expert. Vitex has 20 years of developing and sourcing the right fiber optic and cabling solutions for OEMs, end users, system integrators and network specialists. Contact us to speak to an engineer about your application or to order a sample product for onsite testing.

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