Guide To Data Centre Power

Discover more about managing Data Centre power

In this Guide to Managing Power in Data Centres you’ll discover how Data Centre power works and how to calculate power requirements. Key points to managing Data Centre power and solutions available for better power management.

How Does Power Work in a Data Centre?

Having effective power solutions in a Data Centre is vital, as how much power is used greatly impacts the energy performance of the Data Centre. The largest user of power in a Data Centre is the cooling system and usually the area where the biggest energy cost-savings can be made.

In order to achieve this the Data Centre must have in place a strategic airflow management plan, following the guidelines laid out in the 4R’s of airflow management is a good place to start.

Power used within the Data Centre by the IT equipment usually first gets supplied to Uninterruptable Power Supplies (UPS) which convert and store some of the power to their batteries so that equipment uptime can be maintained in the result of a short-term power failure. Power from the UPS gets feed to the main breakers from where it then gets distributed to the racks. Power within data centre racks is supplied by Power Distribution Units (PDU) and knowing what PDU is needed will depend on the amount of equipment to be plugged in, the amount of energy required by each piece of equipment, whether it requires to be supplying AC (Alternating Current) or DC (Direct Current) power and what level of power management is required.

Calculating Power Requirements for Data Centres?

When it comes to calculating power requirements for Data Centres it is important to understand the requirements of the basic components of electricity:

  • Amps – The actual electrical current being supplied by the power feeds.
  • Volts – Considered as the pressure pushing the amps through a designated path. The higher the number of volts the better the efficiency.
  • Ohms – The resistance that slows the electrical current.
  • Watts – The amount of power that is used by a device.

Calculating each of these components is achieved by using one of the following formulas:

  • Amps = Watts / Volts.
  • Volts = Amps x Ohms.
  • Watts = Volts x Amps.

Knowing these formulas can help make decisions regarding Data Centre power, for instance the specification of PDUs, which will be most energy efficient, how many servers can be powered by an individual PDU, how much capacity is left within each rack for future requirements, how efficient a specific piece of equipment is and what measures might need to be introduced to make the Data Centre power usage more cost-effective.

When calculating power efficiency within the Data Centre, most Data Centres use the Power Usage Effectiveness or PUE metric. PUE was introduced in 2006 by The Green Grid and is a ratio that compares the total amount of energy a Data Centre facility uses (cooling, lighting etc.) against the energy used by the computing IT equipment itself. The ideal PUE is 1.0, and the closer you can get to this figure the more energy efficient your data centre will be. However, PUE can vary greatly from Data Centre to Data Centre based on factors beyond a Data Centre’s control such as the amount of free cooling it can use. So, a Data Centre in a cold climate will require a smaller cooling system than a Data Centre located in a warm climate. Optimising the cooling system is a good starting point for reducing PUE which once done then enables decisions to be made regarding other measures to lower the PUE such as lighting and equipment replacement.

Five Key Ways of Managing Power in Data Centres?

With power being a Data Centre’s biggest asset managing power effectively can improve its efficiency. Identifying these areas can be tricky so here are five key ways of managing power in the Data Centre:

  1. Conduct A Power Energy Audit – Before you can begin managing your Data Centre power you need to know the overall power situation, this can only be achieved by conducting a power audit. Identifying how much power is required by cooling systems, lighting, IT equipment will enable you to calculate the PUE metric and provide a base point from which to work from.
  2. Optimise Cooling Systems – As cooling the data centre requires the most power usage having a strategic airflow management plan that follows cooling best practices will enable temperature set points on the cooling units to be raised or even turned off. In doing so it will enable power cost savings to be made. For every degree Fahrenheit (0.56°C) that the set point is raised it equates to a 4% energy cost saving!
  3. Turn off Idle IT Equipment – Any IT equipment that’s not being used turn it off, even if it’s just over night. Equipment that is plugged into a smart or intelligent PDU can be power cycled at a specific time, or on demand, to ensure the equipment is available again at the required time.
  4. Utilise Power Management Features – If the installed IT equipment has any power management features utilise them. For instances many modern servers offer CPU power management features that optimise the power consumption of the CPU, and as 50% of the power needed to run the server is used by the CPU it’s another area where improving efficiency can lead to energy cost savings.
  5. Use Energy Efficient Equipment – Once you have conducted a power audit you’ll probably identify equipment that is using more power. There could be a number of reasons for this, but if it is because it is an old piece of equipment it may be time to replace it as part of an equipment upgrade program. When new equipment is purchased ensuring that it is energy efficient will help manage power and reduce power costs.

PDU Power Monitoring

Tips for basic power distribution?

Basic power distribution units are available in various formats and choosing the correct one needs careful consideration. Determining how much equipment needs to be accommodated by it will help decide how many outlets they require and whether they need to be single-phase or three-phase PDUs. EDP Europe’s basic power distribution units are custom made and built to match your requirement. They can be horizontal for mounting within the rack space or vertical for mounting to the sides of the cabinet. Features such as ammeter, circuit breakers, individually fused outlets and locking outlets that can prevent accidentally unplugging of equipment can all be included. EDP Europe also able to offer solutions for bespoke power requirements such as power splitter boxes for splitting 63A or 32A power feeds.

What is Intelligent Power Distribution?

Intelligent power distribution units, or smart PDUs as they are sometimes known as, provide power management over IP. They enable Data Centre Managers the facility to monitor power usage through a web browser interface and provide them with power consumption data required to make power management decisions.

For larger installations central management is possible through software applications or integration into DCIM systems. Intelligent PDUs come in different models, there are some that will only provide power usage information for the entire power strip whilst others enable power monitoring down to individual outlets. This is particularly useful in Co-location environments where power being used by individual pieces of equipment may be being billed. Other intelligent power distribution units offer power control, enabling the power to be remotely cycled. This can be particularly useful in unmanned environments where power to equipment may require cycling and can save the expense of sending an engineer to site to do the task. This facility can also be used to schedule power downs and power ups for equipment that is not used regularly or as part of a power management schedule.

Power Backup and Switching Power Sources?

Power failures happen, so having solutions for power back up and products for switching power sources is vital if Data Centre uptime is going to be maintained. Power being supplied into the Data Centre will usually be supplied into large UPS units before it is distributed to the racks housing the servers.  Smaller UPS units can also be installed at rack level to help keep mission critical IT equipment running while the main power source, or power from backup generators, is restored. UPS units are fitted with high capacity batteries which are constantly being charged whilst mains electricity is present. When this fails the connected equipment remains powered up as the supply continues but via the batteries. Most modern servers are fitted with dual power inputs enabling the server to be powered from two separate PDUs or via a PDU and UPS, this provides redundancy should one input or supply fail.  For equipment where there might only be one power input switching power sources can still be achieved through the use of an Automatic Transfer Switch (ATS) or Power Transfer Switch (PTS) as they are also known by. In this case the equipment is connected to the ATS which is then powered by two different sources. In the event of one power feed failing the ATS automatically switches to the second feed to maintain continuity.

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