By: Darren Bonawitz
In this third installment dedicated to discussing power in colocation environments, we will be looking at uninterruptable power supplies (UPS). As mentioned before, these blog posts are not meant to be a comprehensive discussion but rather serve as a starting point and high level overview of things to consider when evaluating collocation facilities.
UPS systems, also known as battery backup systems, condition the utility power to defend against issues such as electrical spikes and also provide emergency power from a separate source when utility power is not available. This allows equipment to operate without interruption until a generator is operational and able to support the electrical load. Good questions to ask the collocation provider include the brand, capacity, minimum guaranteed run-time, redundancy and maintenance program for each UPS system. In addition, if you tour the facility, have them show you the exact unit which will service your unit.
Brand – There are several quality UPS manufacturers suitable for data center environments. Some common brands include (in alphabetical order): APC, Eaton (PowerWare), Liebert, MGE and Sentinel Power. The key is to note that not all UPS systems are equal. Make sure you are connected to a larger data center grade unit, which in my opinion, offers better protection and more robust features. UPS systems can be weak points in a power distribution network so this is not an area to skimp, and you do not want your critical infrastructure tied to smaller off-the-shelf units found in smaller hosting and commercial environments.
Capacity – Measured in kilovolt-amps (kVA) or kilowatts (kW). The difference between kVA and kW is what is known as the power factor. kVA multiplied by the power factor equals the kW.
For single-phase power:
KILOWATT (kW) =
VOLTS x AMPERES x POWER FACTOR
For three-phase power:
KILOWATT (kW) =
VOLTS x AMPERES x POWER FACTOR x 1.73
This tells you how big the UPS is and how much equipment can be powered by it. The size of the UPS needs to be proportional to the size of the colocation area and the corresponding electrical load. For example, if the data center operator states that their average customer utilizes 8kW per rack and they have 100 racks with equipment, it is not a good sign if their one and only primary UPS is a 500kW equivalent unit. Mathematically, they do not have enough power to support their existing customers — let alone your new equipment.
Redundancy- If you have mission-critical equipment collocated, it is important to make sure your provider offers A & B power feeds to your cabinet. If you equipment is not dual power supplied, then consider an in-cabinet automatic transfer switch which has inputs for two power feeds which then output to a single power strip. This will protect you if one feed loses power or one path needs to be taken out of service for scheduled maintenance. Remember that scheduled maintenance is a part of a data center environment, and you need to plan for it. Not everyone needs A & B power, and if you don’t need it, having the option to pass on being supplied a B feed could keep your price down. At the same time, you have to be realistic and realize that you cannot cut costs and then complain about outages (whether scheduled or not) when you elected to not take advantage of the available levels of redundancy offered by the facility.
Maintenance Schedule- Ask to see the provider’s maintenance schedule and report. This is to make sure they are testing UPS regularly and maintaining/replacing batteries, capacitors, etc. as necessary. This can also serve as a qualifier that let’s you know if they are being truthful with you. If the provider does not have documentation of their maintenance records, consider another facility. This is a very common area that data center operators cut corners on. All of 1102 GRAND’s UPS systems and supporting infrastructure are under preventative maintenance contracts and serviced on regular schedules. It is not inexpensive to do this, but we firmly believe in the importance of this and know it helps separate us from many competitors.