Hardware Today — UPSes Heed the Call for Backup

By Ben Freeman (Send Email)
Posted Jul 26, 2004


These days, the need for backup power is a pretty easy sell. Organizational concerns about power outages and terrorism help fuel the need to ensure the juice is always on tap so systems can continue running. This week, Hardware Today surveys the always-on world of backup power in our monthly server room components feature. We'll discuss what to look for as well as jumpstart your comparison shopping by spotlighting two vendors: market standout American Power Conversion (APC) and France-based MGE UPS Systems.

An uninterruptible power supply is a must-have for organizations of all sizes. This week, Hardware Today discusses what to look for in a UPS and offers a jumpstart on comparison shopping with the spotlight turned on APC and MGE UPS Systems.

Uninterruptible Power, Somewhat

UPS: A power supply that includes a battery to maintain power in the event of a power outage. In an outage, a UPS keeps the server powered on long enough for the admin to take corrective action.

In an outage, an uninterruptible power supply (UPS) uses batteries to keep the server powered on long enough for an administrator to take corrective action. A UPS works in conjunction with a backup generator, or backs up critical data and shuts down before the server loses power altogether. Any UPS worth its salt can issue server commands to send out alerts.

Three kinds of UPSes proliferate.

  • Standby power systems (SPSes) use a power inverter, which kicks in to convert DC battery current to AC when the UPS detects a problem with normal outlet power. The switchover from AC to battery, however, leaves a several-millisecond-long gap in server power.
  • Line-interactive UPSes use a flexible inverter/converter unit that charges the battery when the power is on, then converts battery power into AC in case of an outage. This results in a time gap slightly smaller than that of SPSes during switchover.
  • Only online UPSes, the most expensive option, provide truly uninterrupted power. Online UPSes power the server entirely from the battery. Under ordinary circumstances, incoming AC power charges the battery. If power cuts out, the battery simply ceases charging, and the server doesn't know the difference — so long as the battery still contains juice.

APC Product Line Manager Brian Standley downplays the 2 millisecond to 4 millisecond switchover lag inherent to SPSes and line-interactive UPSes, noting, "Reality is, IT equipment utilizes switch mode power supplies that have built-in capacitance to handle upwards of 40-80 millisecond losses of power." He adds, "even with a standby UPS, you will not see interrupted power."

MGE UPS Systems Director of Marketing Jack Pouchet takes a more conservative line, "Cheaper standby UPS systems [provide] basic backup for less-sensitive and less-critical desktop PCs and peripherals," he said, "but are not recommended for protecting core servers or essential storage and connectivity devices."

Bottom line: If you can afford it, use an online UPS; if you can't, take comfort in the fact that servers typically stay powered through brief millisecond gaps in power. Just make sure to test your batteries regularly, as otherwise you won't know they're dead until the power spikes and slams your server.

For New Buyers

Pouchet steers first-time buyers toward an online UPS, where always-deployed batteries provide regulated "digital quality power." Look for hot swappable batteries and the option to upgrade them. In addition, automatic cutover to a redundant power source can be useful for a malfunction, and server communications capabilities are essential.

It is also important that the vendor has factory servicing for its UPSes. "While third-party computer repair options are abundant, the same cannot be said for UPS service," Pouchet said. "Some vendors that specialize in smaller products rely on third-party or depot repair options that can leave the user without power protection for extended periods."

Standley adds that management software should "provide event notification and logging," as well as "automatic, graceful server shutdown in the event of an extended power failure."

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