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High-performance Direct Attach Cables (DAC) offer a very cost-effective, efficient and simple way of connecting between network equipment in a storage area network, datacenter or in high-performance computing environments.
Covered in this article:
+ What is DAC
+ Different types of DAC cables
+ Where can you use DAC cables?
+ Advantages of using DAC
DAC cables are made of end-to-end twinax copper and are pre-fitted at the factory with a transceiver module on each end that provides a direct electrical connection into active equipment. Whilst copper might be seen as out of date in the move to more and more fiber, DAC can still offer a real advantage in different scenarios, with low up-front costs and quick installation, but still with data rates of 10G, 25G, 40G, 100G and 400G.
Due to their copper construction, DAC cables are only suitable for short distances (from 0.5 to 15 meters) and come in fixed lengths with transceivers already attached. However, these features make DAC cables ideal for in-rack and inter-rack connections between routers, servers and switches, with the advantage of low power consumption (<0.3W) and low latency.
Different DAC cable types are available, including direct, breakout along with passive or active to support active and passive switch ports:
A wide range of transceivers in different form factors is available for DAC, including SFP+, SFP28, QSFP+, QSFP28.
The main application for DAC cables is in connecting active equipment together, such as switches, routers, servers and other storage, within or between different data racks.
They can also be used to extend the life of switches and reduce the need to make extensive changes to your existing infrastructure.
The main consideration in deciding which DAC cable to use is the transmission distance alongside the data rate.
The higher the data rate required, the smaller the distance that it can be transmitted over. For example, a 100G DAC can only be used in applications of up to 5 meters, whereas 10G DAC can be obtained in lengths of up to 10 meters.
Data Rate | Form Factor | Length Available |
---|---|---|
10G | SFP+ | 0.5m to 10m |
25G | SFP28 | 0.5m to 5m |
40G | QSFP+ | 0.5m to 7m |
100G | QSFP28 | 0.5m to 5m |
When should you consider DAC cables over fiber optical cabling? DAC cables do offer some real advantages in applications where the limitations of their short distance allow them to be used.
Conclusion
DAC is the lowest cost point-to-point solution for high data rates. With virtually all switch vendors supported, plug and play interoperability and hot-swappable with fibre-optic modules, DAC enables you to meet the changing demands of the datacenter flexibly and reliably.
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