Dual-Power Feeds in Data Centers

Things like always-on technology, streaming content and cloud adoption are creating high demand for efficient, resilient and fast data centers that never let us down.

To meet these needs, dual-power feeds – two independent electrical feeds coming into a data center from the utility company – are becoming more common to reduce the chance of a complete outage (or not having enough power). This type of power set-up is often seen in Tier 4 data centers. If one of the two power sources suffers from an interruption, the other source will still supply power.

Generally labeled “A” and “B” feeds, each power source has not only its own utility feed, but also:

  • A backup generator
  • A switch that alternates between A and B feeds
  • Electrical and distribution switchboards
  • An uninterruptible power supply (UPS)
  • A power distribution unit (PDU)
  • Rack-level PDUs

At any one of these points along the chain, failure can occur. A true dual-power feed means that there are two separate sets of these components operating independently, reducing the likelihood of downtime due to failure.

Today, most mission-critical IT equipment, such as servers and switches, are also designed with at least dual power supplies. When everything is running normally, the equipment pulls power equally from both power feeds. In the event of an outage, however, the IT equipment can automatically switch all power to one feed or the other.

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Network Upgrades: Utilizing Parallel Fiber Cabling

It comes to no surprise, that enterprise and consumer demands are impacting data centers and networks. As speed requirements go up, layer 0 (the physical media for data transmission) becomes increasingly critical to ensure link quality.

Numerous organizations are looking for an economical, futureproof migration path toward 100G (and beyond). Multimode fiber (MMF) cabling systems continue to be the most popular, futureproof cabling and connectivity solution.

Both duplex and parallel cabling are options for network upgrades. A few weeks ago, we discussed duplex MMF cabling. In this, we’ll discuss parallel MMF cabling.


Parallel Fiber Cabling

When transceiver technology can’t keep up with Ethernet speed requirements, the most obvious solution is to move from duplex to parallel fiber cabling.

Although using BiDi (bi-directional) and SWDM (shortwave wavelength division multiplexing) transceivers can reduce direct point-to-point cabling costs, they do not support breakout configuration (e.g. 40G switch ports to four 10G server ports), which is a very common use in data centers.

According to research firm LightCounting, approximately 50% of 40GBASE-SR4 QSFP+ form factors are deployed for breakout configuration; the other 50% are deployed for direct switch-to-switch links.

As a matter of fact, 40G QSFP+ and 100G QSFP28 are the most popular form factors used for Ethernet switches in data centers. QSFP (quad small form-factor) is a bi-directional, hot-pluggable module mainly designed for datacom applications. QSFP+/QSFP28 has a 2.5x data density compared to SFP+/SFP28, using four parallel electrical lanes. The optical interface is a receptacle for MPO female connectors. Four fibers (1, 2, 3 and 4) transmit the signal; the other four fibers (9, 10, 11 and 12) receive the optical signal.

QSFP transceivers, paired with parallel fiber connectivity with a one-row MPO-12 (Base-8 or Base-12) interface, can support flexible breakout or direct connection.

  • 40G/100G direct links are typically used in switch-to-switch links, which can be supported by duplex or parallel fiber cabling.
  • 40G/100G Ethernet ports can be configured as 4x 10G or 4x 25G ports to support 10G/25G server uplinks.
  • 40G/100GBASE-SR4 transceivers only use eight fiber threads in an MPO-12 connector; therefore, Base-8 is a cost-optimized cabling solution that allows 100% fiber utilization.

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