Mission Critical - Winter 2008 - (Page 69)

Data Center Racks continued outlets required to power the entire IT load within the rack. Equipment can have multiple redundant power supplies with each requiring one or more power connections. A rack with several blade servers will require low number of high-power outlets, while a rack with several 1U servers will require high number of lowpower outlets. Features to Require on Rack-Mount PDUs Power distribution units that have metering as well as switching capabilities can help ensure the highest availability levels for mission critical equipment. When new equipment is connected to a PDU, the plugged-in loads are susceptible to tripped breakers or fuses. To minimize the chance of overloads, metering capability plus the capability to set current thresholds within the PDU is important. If the PDU has several branch circuits ing so the circuit’s current limits are not exceeded. Sequencing also allows applications running on several servers that are dependent on each other to be started or shut-down in a specific order to avoid issues. • Electronic overcurrent protection. When current thresholds are exceeded on a branch circuit, many switched PDUs can lock unused outlets on that branch. Therefore, no additional equipment can accidentally be plugged in and continuous availability to the powered loads is ensured. Remote Management To maximize monitoring and control features and ensure a “lights-out” data center, switched and metered PDUs should be remotely manageable. When evaluating the equipment, consider the following: • Does the remote management strategy of the PDUs align with tools used to manage other IT devices? • Do the PDUs provide an out-of-band management option? In-band management tools are great, but their limitation is the vulnerability to problems from the very devices they manage. • Does the remote management tool provide a global integrated view of all PDUs? • Does outlet access follow secure authentication schemes? • Does the remote management tool automatically discover all attached PDUs? • Does the tool provide grouping capabilities for outlets? Grouping allows power control of multiple outlets together, useful for when a server with multiple power supplies is hung. By recycling power to all power supplies together, grouping ensures the power to the entire server gets recycled. Data center operators need to pay close attention to determining the anticipated loads within the racks because of rising power densities. or is three-phase, metering capability should be available for all branch circuits or phases separately. Nameplate current ratings for most IT equipment is overrated. Metering capability can provide a gauge of the actual power draws of IT equipment. This information could allow operators to right-size upstream electrical infrastructure improving the efficiency of the entire power chain Non-responsive servers or network equipment is a common issue. Switching capability, defined as the ability to remotely recycle, turn on or turn off power, can help minimize downtime caused by hung equipment. Reducing the number of trips to the physical location of equipment also helps lower operational costs. Several switched PDU solutions have additional features that can improve the availability of the loads: • Sequential startup & shutdown. IT equipment draws a current higher than normal operation at startup called the “inrush current”. Unless the circuit is capable of handling the inrush of all equipment, starting all loads within a rack at once can lead to tripped upstream breakers. Switched PDUs allow outlet turn-on sequenc- Summary A well-planned rack-level power distribution is important to ensure continuous power to all IT equipment as well as to monitor and control the power consumption. Proper consideration should be given to the electrical, physical and feature characteristics of the PDUs. Electrically, IT equipment should operate within the 200 – 250-V range when possible. For loads within a rack above 5 kW, a threephase PDU is best; a single-phase PDU for loads below 5 kW. Physically, PDUs should be easily installable and have the appropriate number of outlets to power all equipment. Remotely manageable PDUs with switching and metering capabilities provide the ideal feature set for highest levels of availability as well as efficiency. ■ ◗ REPRINTS OF THIS ARTICLE are available by contacting Jill DeVries at devriesj@bnpmedia.com or at 248-244-1726. Winter 2008 www.missioncriticalmagazine.com | 69 http://www.missioncriticalmagazine.com

Table of Contents Feed for the Digital Edition of Mission Critical - Winter 2008

Mission Critical - Winter 2008 Table of Contents Editorial: What Have We Been Doing? Cronin’s Workshop: Imagining the Perfect Data Center Power And Cooling Solution Digital Power: The Next Edge in Business Resiliency Zinc Whiskers: Keeping Up With The Green Movement Mission Critical Care: Shipping, Staging, and Installation Legal Perspectives: “A Reliable Energy Supply Is Key to Data Center Success” Continued Payback, Instant Protection Beyond the Nines The Green Information Technology Revolution Health Care Network Offers Glimpse of the Future of Backup Power High-Density Data Centers – Discuss, Design, Deploy High Performance Data Centers Call for Innovative Cooling Techniques More Data in the Data Center Five Considerations for Powering Data Center Racks New Products Industry News Events Classifieds Letters Ad Index Datacenter Wiki: wiki-Mission Critical

Mission Critical - Winter 2008

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