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How Direct Attach Cables (DAC) are used in a Datacenter?

CBO
2017-04-07 13:16:00 / Direct Attach Cable / Comments 0

In the modern and ultra-high tech Datacenters of today, more bandwidth is needed and used to support the latest demands in the Networking world especially in a server-virtualization environment where multiple virtual machines are being combined on a single physical host server. To be able to accommodate the growing number of operating systems and applications and at the same time providing scalability and reliability, virtualization requires noticeable increased data transmission rates between the servers and the switches in the Datacenter.

At the same time the networking devices, and the pure daily Internet use, have dramatically increased the data that has to be transmitted throughout the Datacenter including the Storage Area Network (SAN) and Network Attached Storage (NAS) environment. According to some researches done in the past couple of years, the amount of data transmission in the world is growing astoundingly, more than 20% in only 5 years. Accordingly the leading IT managers are looking for ways to reduce the cost of implementing the newest technology and at the same time provide the stable Network of tomorrow.

With these thoughts in mind the leading manufacturers started developing a new technology that would be able to meet these requirements. This are the Direct Attach Cables or DACs. This is a high density and low power consumption technology that would allow to create an in-rack 10GB/s solution between servers and switches. Today these Direct Attach Cables are used to transmit huge data transmissions in Datacenters mainly between switches, servers and storage devices. Because of the way they are designed, using the same ports as the Optical transceivers do, they have become hugely popular in Datacenters.

Direct Attach Cables are twinax copper cables that have an Transceiver connector type at each ending of the cable. They use the same ports as an Optical transceiver and they canbe used for Ethernet, Fibre Channel and Infiniband applications. These cables are mainly divided in three separate types that are most commonly used:

DAC Variants

  • Passive Direct Attach Cables - Because these cables are passive and they lack in an active circuitry component they can provide up to 10GB/s speeds up to 10 meters. Also bigger bandwidth cables for up to 100GB/s with shorter reach are available.
  • Active Direct Attach Cables - With the help of the active circuitry component these cables can reach up to 15 meters providing 10GB/s or up to 10 meter with the 40GB/s solution. Other than the active circuitry component this cables are designed in the same way as the Passive Direct Attach Cables.
  • Active Optical Cables - These cables incorporate active optical and electrical components which can reach up to 100 meters on Multi-mode fibers. These cables can also be used as breakout cables satisfying the various needs of Datacenters. What is also available for the DAC solution from 40GB/s upwards.

These cables are most commonly used for short reach direct connection applications. They are used in Equipment Distribution Areas where the racks are the home of the end servers and where the cabling is terminated on patch panels. For the interconnection between racks these cables are used to connect servers to switches, switches to switches or storage devices to switches. They use an electrical to optical conversion on each cable’s ends which provides higher speed and low latency without sacrificing compatibility with the most standard optical transceivers. With the fast growing 10GB/s Ethernet solutions these cables are mainly used in the SFP+ Form-factor for interconnection between switches and storage devices in the same rack. However in the near future the 25GB/s SFP28 Direct Attach Cables will start substituting the 10GB/s Direct Attach Cables making room for more bandwidth for core switches. These 25GB/s SFP28 Direct Attach Cables are already available on the market.

Das BlueLAN®-Sortiment von CBO bietet verschiedene Varianten von kostengünstigen Twinaxial Direct Attach Kabeln, als aktive oder passive Variante, mit verschiedenen Steckverbindern an, die in der Lage sind, die neuesten Hochgeschwindigkeitsnetzanforderungen zu erfüllen. QSFP, QSFP28, SFP28, SFP+, QSFP Breakout und IB4X. Alle Kabel haben eine 5-jährige Garantie mit lebenslangem Support.


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