We all know that a UPS (uninterruptible power supply) is a device that keeps your equipment running for a short time when the primary power source has been lost. What may not be known is that there are a variety of other problems that a good UPS may solve, and a variety of UPS types to choose from.

A UPS may have one or a series of batteries that keep the power flowing even through a blackout. It can also provide protection against surges, spikes, sags, and line noise. A UPS can be more than just a safety net: it can regulate the power that comes from your wall socket. The UPS can ensure all your 240-volt power devices always receive clean and smooth power.

Most UPSes ship with software that will let system administrators monitor the status of the UPS from a remote location via a network node or Web. Some software can also notify users when there is a problem. If the power does not come back up before the UPS is depleted, the software can initiate a system shutdown.

The capacity of a UPS can be measured in power (measured in volt-amperes or VA) and energy (measured in watt-hours). Power determines how much equipment the UPS can operate, and energy determines how long the UPS can operate the equipment. All the UPSes in this roundup use some sort of sealed lead acid battery. These batteries’ rated lifetime is three to six years, and as they age, runtime also gradually declines.

Software plays an important role in shutting down your equipment. UPS software works by polling the UPS then posting all of its operating parameters such as battery capacity, input voltage, output voltage, and battery voltage. Some software will let you schedule a system shutdown, graph any power problems, and schedule events and create multiple logs. Information is relayed between the UPS and the computer through an RS-232C serial port or network connection.

Power Problems: Cause & Effects

• Spike: Also referred to as an impulse, a spike is an instantaneous, dramatic increase in voltage. Akin to the force of a tidal wave, a spike can enter electronic equipment through AC, network, serial, or phone lines and damage or completely destroy components.

  Spikes are typically caused by a nearby lightning strike. Spikes can also occur when utility power comes back on line after, for example, having been knocked out by a storm or a car accident.

  Catastrophic damage to hardware can occur and data will often be lost.

• Surge: A surge is a short-term increase in voltage, typically lasting at least 1/120 of a second.

  Surges result from the presence of high-powered electrical motors, such as air conditioners, and household appliances in the vicinity. When this equipment is switched off, the extra voltage is dissipated through the power line.

  Computers and similar sensitive electronic devices are designed to receive power within a certain voltage range. Anything outside of expected peak and RMS (considered the average voltage) levels will stress delicate components and cause premature failure.

• Sag: Also known as brownouts, sags are low mains voltages, which can last from 20 milliseconds to several hours. They can sometimes be seen as a dimming of lights. This is the most common power problem, accounting for 87 percent of all power disturbances according to a study by Bell Labs.

  Sags are lower-than-normal voltage from the local substation, often during particularly hot or cold weather, and are usually caused by the start-up power demands of many electrical devices (including motors, compressors, elevators, shop tools, etc.)

  A sag can starve a computer of the power it needs to function, and cause frozen systems and unexpected system crashes which both result in lost or corrupted data. Sags also reduce the efficiency and life span of electrical equipment, particularly motors.

• Blackout: Blackouts are total loss of power for a period between 20 milliseconds and many hours.

  Blackouts are caused by excessive demand on power, or by storms, car accidents, backhoes, earthquakes, and other catastrophes. Loss of power within buildings can be due to overloads or faults blowing fuses or activating circuit breakers. A blackout results in loss of data in RAM or cache, possible loss of File Allocation Table (FAT) which can result in total loss of data stored on drive.

• Noise: More technically referred to as Electro-Magnetic Interference (EMI) and Radio Frequency Interference (RFI), electrical noise disrupts the smooth sine wave one expects from utility power.

  Electrical noise is caused by many factors and phenomena, including lightning, load switching, generators, radio transmitters, and industrial equipment. It may be intermittent or chronic. Noise can introduce glitches and errors into executable programs and data files.

Battery Life

Many vendors give a fairly broad rating of battery life, (generally three to six years) which seems like a fairly large window until you consider the effects the environment can have on batteries.

Ideally, batteries should be run at 25Ã,°C to give greatest battery life. There are a number of formulae that attempt to calculate the effect of temperature on batteries. One such formula says that every 8.3Ã,°C above 25Ã,°C will reduce the battery life by 50 percent. Another is that for every 5Ã,°C above 25Ã,°C battery life decreases by 1 year.

Both of these formulae are quite similar, and clearly reflect the need for adequate cooling around your UPS, especially when they are mounted in a rack. For example, in some of our testing of last month’s 1RU Web servers, the systems reached temperatures of 50Ã,°C, which is well outside the operating conditions of these UPSes.

Small UPSes

APC PowerStack 450

The PowerStack 450 was the only 1RU UPS submitted for this review, and it is quite a nice unit given the limited space and the limited budget it falls within. This is a simple UPS with four female sockets and a serial port on the back. The display is limited to four individual LEDs for mains, battery, system overload, and replace battery.

The run time of just over 20 minutes was the shortest of all the units tested, but this is generally long enough to beat all but the worst of blackouts, and probably has room to grow. If this UPS was to be used in a network distribution cabinet, it would provide more than enough support for a number of devices, but the main shortcoming would be the lack of power outlets available. Hot swap batteries are a real bonus in this price range. The running cost score was an acceptable US$36.37 per minute, which is fairly good for a low entry price unit.

The PowerChute Plus software is very simple to use, and provides at a glance all the information you really need, while underneath is an excellent level of customisation that is well designed and laid out.

APC Smart-UPS 700

The Smart UPS 700 brings us into the “smart” level of the APC range, with various options including remote boot modules, network cards, environmental monitoring, and multiple serial ports. This 2RU unit also has nearly three times the battery life of the PowerStack 450 for less than twice the price.

The front panel display is much friendlier than the 450, with five-LED bar indicators for battery charge and load, as well as LEDs for trim (surge protection), boost (sag correction), online, overload, on battery, and replace battery.

The 700 shipped with an optional Network Management Card (AP9617 RRP $647) that allows network administrators to control the UPSes via various protocols like Telnet, HTTP, FTP, and SNMP. Using the Network Management Cards, you can monitor and configure the UPS to shut down and reboot your computer systems, send e-mail alerts, and view the event log. The Web interface was very easy to use, and the menus were clear and helpful. At 62 minutes, battery life was easily sufficient to handle a few switches and would happily cope with a couple of small servers or high-end routers as well. Running cost was close to the best at $16.76 per minute.

Sola UPS 520RM 750

The Sola 520RM is remarkable amongst the units tested in that it was the only UPS to have standard Australian 10A power sockets on the rear, rather than female IEC-320 10A sockets. This makes plugging units in very easy, as you already have all the cables you need, rather than searching out IEC-320 10A male-to-female cables. The front panel consists of an LED for AC in, which blinks when the UPS is bucking (reducing) or boosting (increasing) the input voltage. A second LED indicates whether the unit is operating on battery or not, and the remaining four LEDs indicate either the percentage battery charge or the percentage load on the unit. These LEDs also blink to alert you to alarm conditions.

The Sola 520 has a BestDock communications slot, which can accept an optional BestLink SNMP/Web adaptor (which was not supplied for testing).

The Sola UPS has a great expansion advantage; if you were to need more than the standard three power outlets, you could easily plug a power board into the UPS and run the devices from that. It is much more difficult to do that with an IEC-320 10A connector. Also on the rear of the unit is a network surge protector, which can be used to protect your equipment from a surge via your Ethernet cable. This is often used where Ethernet is run from another building, or another part of a building, and might be subject to a surge (eg, a lightning strike).

The CheckUPS II software supplied with the 520 does a good job of controlling the UPS, and has a very informative display, but it is missing a percentage charge indicator, which makes it difficult for us to tell when the batteries are fully charged. The tested battery life was an acceptable 50+ minutes, which means there is plenty of room for expansion. This also gave it the best running cost score of just $15.55 per minute.

Upsonic Pro Power PLUS 700

The Upsonic Pro Power plus 700 has a simple front panel layout, consisting of a combined bar-style load and battery level indicator, and additional LEDs for fault, bypass, battery, inverter, and line input. To switch between load level (the default display) and battery level, you need to press the on/off button for one second to put the unit into test mode. The only problem with this is that pushing the button for two seconds will turn the unit off completely, which is asking for trouble.

There is a SNMP slot in the rear of the unit, but it is only briefly mentioned in the very generic manual. When we removed the cover, there seemed to be nothing to plug a card into. Upsonic sent us an external Net Agent II network adaptor, which we were able to connect up to the UPS and plug into our test network. This device allowed us to set a range of notifications, but it was rather difficult to use and quite confusing to install.

On the rear of the unit there are 4 x 10A sockets, though we did have a problem with two of them—the contacts didn’t quite meet correctly, and sometimes, with some plugs, we had to wiggle the cable a little to get a proper connection.

There is an external battery connector for adding an extra runtime and phone protection socket, which seems a little odd in a unit that is going to be in a rack, though you might use it to protect a dial-in line.

Battery life on the 700 was the best of all the units tested, keeping the three switches running for over an hour and seven minutes, but the high purchase price means this unit has a running cost of $25.89 per minute in our tests.

The Upsilion 2000 Software that came with the unit was excellent. A small daemon runs in the system tray and when the application starts up, it connects through this to the UPS. There is a large range of display options and an even larger array of configuration options in terms of notification of problems and shutdowns.

Larger UPSes

APC Smart-UPS 3000

The APC Smart UPS 3000 is the big brother to the 700, and features almost exactly the same features but has much longer battery life in a 3RU form factor. The front panel display is identical, as is the software, and the accessories are interchangable. On the rear, the only difference is that there are eight 10A female power sockets instead of the four on the 700.

Battery life was the best of the large UPSes, lasting over an hour and 20 minutes with the test server and switches, which means it would easily handle a fair-sized group of rackmount servers. Running costs came in at an excellent $46.93 per minute. The same network adaptor is still an optional accessory, but for only around $650 it would be unusual to pass it up, given the usefulness when dealing with multiple servers that may need to be shut down.

Powerware 5125 3000e RM

The Powerware 5125 is part of an extremely scalable power backup solution. This unit contains 10 12V batteries in a 2RU case, but has the capability of having up to four extended battery modules (EBMs) attached for much greater backup capacity.

The front panel is relatively Spartan, with a five-level load indicator and LEDs for error, battery mode, battery service, site wiring fault, and power on. There is no indicator of battery life on the unit since there may be extra EBMs connected to it, which would make calculations difficult.

One useful addition to this system is a test/alarm reset button, which allows you to test the unit or silence the beep in case of an alarm.

Other than more EBMs, this unit supports any of a series of X-Slot modules that consist of a six-port serial module, an Ethernet/Modem/SNMP module, an SNMP/Web Module, or a USB module. Unfortunately none of these modules shipped with the unit for testing.

The rear of the unit has three sets of three 10A sockets, with each set having its own circuit breaker. You also have the option of shutting down each group separately, in the event that the uptime of some equipment is more important than others.

The 5125 came a close second in the battery life tests, and came out with the best overall rating in the return on investment scale with a running cost of $44.72 per minute. The LanSafe III software included in the package provides a good visual indication of the state of the UPS.

Upsonic Pro Power PLUS 3000

The Upsonic Pro Power Plus 3000 is almost exactly the same as its smaller brother, the 700. Overall the unit is quite a bit bigger, increasing to 3RU and an extra 100mm deeper to accommodate the extra batteries. The front panel and software are the same, with the major differences being the rear of the unit, which now supports six 10A sockets. This is probably a couple short of what we would like to see in a unit this size.

Again, accessory information was limited, and though an external network option is available, we would really like to see it inside the system unit—it either has to hang around at the back of the rack or sit on top of the UPS and take up another RU.

The battery life in the test unit was quite poor, lasting only 33 minutes, which gave it a running cost of $153 per minute. To be fair, we feel this unit may have been a test unit for some time, and the batteries might have suffered the effects of temperature and a generally hard life. The excellent Upsilion 2000 software was also included in this package.

Scenarios and testing

Scenario 1:

Company: Quimby Demolitions
This company needs a small rack-mountable UPS to run a total of four switches.
Approximate budget: $1000
Requires: One rack-mountable UPS with four power ports.
Concerns: Maximising uptime in the event of a power failure is the company's main concern. Minimising rack space is also an issue; the company would prefer a 1U device, but 2U is acceptable.
Best Solution: APC Smart-UPS 700
Qumby Demolitions would be best served by the APC Smart-UPS 700. This unit has all the features you need, including the option of internal networking. The software is very good and battery life, while not the best, was very close. The Sola 520 ran a close second; it would have been great if we could have seen it's networking capabilities.

Scenario 2:

Company: MadCat Internet
This ISP needs a rack-mountable UPS to run seven servers and three switches.
Approximate budget: $5000
Requires: One rack-mountable UPS with 10 power ports.
Concerns: The company wants to be sure the UPS will provide enough power to let all the servers shut down gracefully in the event of a failure. The company will also look into how the UPS communicates with the servers, the UPS management software, and the availability of hot-swappable parts.
Best Solution: APC Smart-UPS 3000
The APC would once again be the best choice here, though closely followed by the PowerWare 5125. Both systems have excellent running time and cost-per-minute ROI, but the APC wins with slightly better software and the fact that we have actually been able to see and test its network solution.

How we tested

All UPSes were plugged in and charged up for 24 hours before testing.

Small UPSes: We attached three assorted articles of network gear: a 10Mbps switch, a 100Mbps hub and a gigabit switch to the UPS and timed the battery life.
Scenario 2: We attached the abovementioned hubs and switches plus an Acer Altos 1200 server and an old Digital 14in monitor to increase the load.
Battery life was timed by recording the timestamp on a system while pinging a Testlab server through the gigabit switch. As soon as the pings stopped, the clock was stopped and the runtime calculated.
Each server was tested twice and the results averaged.
Interoperability was rated on operating system support, easy-to-read display, and software.
Futureproofing scores were based on replaceable batteries, the ability to add batteries, and the availability of a network module.
ROI was calculated based on the cost per minute of uptime provided by the UPS.
Service dealt with the duration and terms of the warranty.

The September issue of Australian Technology & Business magazine contains benchmarking tests on the products outlined in this article. For information on how to subscribe to this magazine, visit this page.

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