Back in December, I blogged on the topic of calculating power requirements for your comms room. At the time of writing, I was specking up new uninterruptible power supplies (UPS) for one of our data centres. The UPS units in place at the time were no longer capable of providing the power required to keep things running for a reasonable amount of time in the event of mains failure. Add to this the fact that they had no management features; it was time for an upgrade.

The first step was going over system and device maps to decide which required uninterruptible power and which could be done without in the event of a complete power failure. Next, I used the manufacturer-supplied specifications of each device or power calculators to work out the maximum requirements of each device / system. My final figures came to around 14,000VA / 60A.

Now that I had an idea of how much power needed to be supplied, I needed to compare various UPS systems capable of supplying the correct amount of juice. After studying manuals, Web guides, tons of marketing blurb, and taking on some personal recommendations, I finally decided to go with the APC Smart-UPS RT.

The Smart-UPS RT range are rack-mountable units available in sizes from 2U/1000VA to 6U/10,000VA. External batteries can be added to increase runtime; voltage and frequency are regulated; and mains input can be either one or three phases.

The management features of these UPSs are particularly impressive, especially considering that the units are not overly expensive, and all of these features are in the box as standard:

  • DB-9 RS-232 serial interface
  • RJ-45 10/100 Base-T network interface
  • SSH/Telnet access
  • Web configuration tool
  • PowerChute Network Shutdown client for Mac/Windows/Linux
  • SNMP and Email notifications
  • Environmental Monitoring (temperature triggered alerts and shutdown)


I went for two 8000VA units, capable of providing 2000VA more than the peak requirements. This allows some room for expansion without having to worry about power capacity. At 100KG each, these were not easy to get into the basement, which unfortunately, has no goods lift. Luckily, the four internal lead acid batteries could be easily removed and the units carried down the stairs a piece at a time. Installation was a breeze; the accessory packs were all complete (no missing bits!), and the instructions straightforward.

Having all systems in the date centre powered down for a pre-scheduled amount of time also provided a rare opportunity to review all cabling and power distribution. I rewired all servers and replaced the existing power blocks with APC Switched 1U / 16A / 8xC13 outlet Power Distribution Units (PDUs). These units have a highly visible panel on the front that display real-time consumption figures; they also have serial, SSH/Telnet, and Web interfaces,which–much like the UPS units–allow full control of the internal management functions. Power on/off delays, current monitoring, alarm thresholds, e-mail/SNMP notifications, and direct control of each outlet give full control of power at a per-device level. As with the UPS units, the PDUs were easy to install and configure, and the Web interface was extremely intuitive.

The new UPS and PDUs have now been installed and running for almost one month, and I have to say that I’m extremely happy with the results. Notifications work like a dream; the UPS instantly sends e-mails to my Blackberry upon any status change or alarm events. While typing this, I received an e-mail to inform me that the weekly self-test has been performed and passed. I’m equally as happy with the new distribution units that also e-mail me directly upon any port state change–vital information if you’re trying to remotely work out why a machine has just died.

Knowing that I can have full confidence in the centres’ power distribution and backup resources is something that makes it easier to sleep at night. Since I’m so pleased with the APC equipment, I have to wonder what power equipment others are using? Do you have opinions on other equipment manufacturers (good or bad); are you using UPS-only or generator-supported, monitoring systems, and fully automatic recovery? Why not leave a comment and let us know what you’ve been working on…