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UPS for all seasons: 6 appliances tested By Michael Palamountain, Technology & Business magazine November 19, 2004 URL: http://www.zdnet.com.au/reviews/hardware/peripherals/soa/UPS-for-all-seasons-6-appliances-tested/0,139023417,139167262,00.htm
 
Suffering from blackouts, brownouts, or sags? How about bushfires, floods, or cyclones? Then maybe you need a UPS. We review six UPS appliances.A few years ago this would not have been such a serious an issue as over-sized power supplies protected our machines from a certain amount of trouble. However not so with my current machine. The power supply itself survived the disaster (I could just hear it saying, "That'll teach you to make me work so hard"), but I lost the RAM, CPU, and both hard drives. Foolishly, I had backed up certain information on the second disk, but did not have everything on removeable media for offsite storage (although I thought I did). As a result, I am still discovering exactly what I have lost, and am still trying to replace it. The worst of it is, all of this trouble could have been prevented by using an uninterruptable power supply (UPS). Emergency power is online The job of a UPS is basically twofold. Firstly, it should ensure that the electric current reaching your equipment is "clean" -- and I don't mean "green" but rather that it matches the quality intended by the utility and that required by your equipment. Clean power can be achieved by using a line conditioner. Spikes, sags, surges, noise, and even frequency variations can be detrimental to the effective live of electronic devices of all kinds. Spikes and surges are momentary and prolonged increases in voltage respectively, these can overload circuitry, blowing fuses -- or worse -- delicate electronics. A surge protector will protect you from such troubles, but you might still be caught out be the opposite problems: sags and brownouts. Sags and brownouts are low voltage problems, which are also quite capable of stressing electronic circuits. Electrical noise can interfere with proper equipment function (unshielded communication lines are particularly susceptible to such interference). Fluorescent lights, electric motors, and high-voltage cables can all cause noise, so it is worth taking a careful look at the relative positioning of all electrical equipment and the cabling that supports it. Don't leave cables in messy bundles or coils, avoid piggy-backing power-boards, and try to use the right amount of cable for the job. Besides the problem of noise, messy cords can be a potential fire hazard. Secondly, in the event of a total power failure (blackout), the UPS should continue to run on battery power until either, (a) the power supply returns to normal, or (b) the user is able to save data and shut down the equipment gracefully, or transfer to an alternative power source, such as a generator. Once power is restored the UPS automatically recharges its batteries. A UPS will contain circuitry for line conditioning as standard. In the event of an extended power shortage -- say storm damage wipes out power-lines in your area -- then a UPS may not be able to protect your business by itself. In critical situations you might consider a generator to back up your UPS. This way, if you cannot afford to stop work when the UPS battery runs down, the UPS can signal the generator to take over from the mains supply (or switching can be manual for that matter) before the battery capacity reaches zero. Hospitals, for example, make use of generators to backup their essential services. Check the generator periodically to ensure that it is well maintained and that there is an adequate supply of fuel on-site. The price of failure
A 3000VA UPS could support about five servers. At about AU$6000 per server that's AU$30,000. Now how much value do you place on the data stored on those machines? How many person hours will it cost to replace or repair hardware, load backup data, and then redo the work that was lost between the last backup and the power crisis that has stopped your business in its tracks. (You do have recent backups of all your data on removeable media don't you? And that media is in a safe place, yes?) Even if no physical damage is done, even if no data is lost, consider the disruption to the work day caused by a brownout that causes every server to reboot in the middle of a transaction or backup procedure. Workers will get irritated and thus their productivity is likely to be further reduced. Isn't it worth spending three or four thousand dollars to protect your investment? With regard to return on investment, I'm tempted to give every machine five stars simply because whichever one you choose, your UPS is vital insurance for your equipment and data -- I cannot stress this enough. How big is yours? UPS power ratings are given in terms of Volt Amps (VA). To determine the size you need simply multiply the supply voltage (probably 240V) by the current drawn by the equipment needing protection. For example, four computers drawing 830mA from a 240V supply require an 800VA UPS (0.83A x 240V x 4 = 796.8VA). This month's review looks at rack mountable UPSs for the server room, rated at 3000VA. Please note that devices of this size use 16A power connectors, so ensure that your site is set up to cope with 16A plugs before purchasing. Battery run-time is dependent on the load. If the UPS is only supporting half of its rated load it may operate for up to three times longer before losing power. Typically, UPS specifications will claim about 15 minutes runtime on half load and only about five minutes on full load. Realistically, the load will probably be somewhere in between -- you don't want to push the limits of the UPS (and you should allow for expansion of your current needs), and you don't want to pay for an excessively large UPS. Should you, by chance, overload your UPS you'll know about it, because it will sound an alarm and flash one of its LEDs frantically at you. Often, additional external battery packs are available which can be used to expand system capacity without totally replacing the UPS (more later). This is particularly useful in situations where it is not practical to shut down all systems with the typical five to 10 minute window. It is also generally a good idea to avoid running a laser printer via a UPS. Such printers are extremely power hungry and thus greatly increase the size requirements of your UPS. Energy guzzlers can always be protected by a separate line filter (without battery backup). UPS types
Line interactive systems send part of the available mains power through the inverter -- enough to keep the battery charged. The battery can then support the main supply during a sag, or take over completely during a blackout. Sometimes manufacturers can be a bit loose with the terminology and label these as online, so take care. The load cannot be completely isolated from variations to the mains power without switching to the battery. Again a filter is required. With online models (also called double-conversion), mains power constantly runs through the inverter, which supplies the battery. All power entering the UPS is rectified and reconstructed as a purified waveform (without need of further filtering) before reaching the load (Figure 1c). Since all power is running through the inverter and rectifier at all times these components need to be very robust, thus increasing the price of this type of device. Online UPSs provide the most complete protection to networked computer systems. Communications, Management Power failures and fluctuations can occur at any time and you may not be there to shutdown your equipment should this be necessary. Fortunately UPSs normally come with hardware and software that automates shutdown prior to the battery being fully drained. Three basic interface methods are available: Serial port, USB, and Web based (SNMP). The interface, whichever type is chosen, allows the UPS to inform the system administrator of any variations in the state of the electricity supply and recommend that shutdown procedures be initiated. Automatic shutdown generally occurs only after users have been given a warning to shutdown manually. Before purchasing a UPS you will need to consider the most appropriate control method. Do you have serial or USB ports available? Are there any possible hardware conflicts? Do you understand how to make the most of the option you have chosen? Will it interoperate with your existing network management system (NMS)? Remember that your UPS need to support not only the servers, but also the associated administration workstations and other essential devices (switches, routers, external drives) that need to maintain power in the event of a mains failure. Particularly in the case on an SNMP device, switch protection is vital. What's the point of your server trying to communicate with the NMS if the network itself is compromised? Batteries AND Runtime Typically a UPS uses sealed lead acid (SLA) batteries. These are basically like a car battery that is sealed to prevent leakage. They don't need to be topped up, but, like any battery, they can wear out in time and thus require replacement. In the event that the batteries need to be changed it is normally possible to do a hot-swap; that is, the batteries can be changed over with out powering down the system first (and thus interrupting the hardware you are trying to prevent from being interrupted). Advanced battery management (ABM) ensures that battery life is as long as possible. UPS batteries are charged to about 90 percent (sometimes less) rapidly and then allowed to charge fully at with a "trickle charge". The battery is then allowed to rest a while before being subjected to any further charging which might be required due to usage. Typically during a power outage, batteries will last for five minutes when the UPS is fully loaded, increasing to around fifteen minutes for a half-loaded unit. It may well be that this is totally inadequate for your purposes. What happens if servers are in the middle of a lengthy process (such as a CAD/CAM rendering), which cannot be interrupted, or perhaps an urgent job that must be completed now or sooner? Fear not because external battery packs can normally be added to these heavy duty UPSs. As an example, both Powerware and Liebert claim that their machines can run for two hours with a 75 percent load when backed up with four external batteries. Liebert UPStation
Nikko Vanguard
What management options are offered by the devices? Futureproofing What is the expansion potential of the machine, and what are its networking capabilities? ROI What value for features are offered? Service How long is the warranty? The longer the better. Each UPS was tested driving a single Apple Dual xServe G5 400W server and an 80W monitor. The basic routine was:
Sample scenario
This company wants to provide a UPS supporting a single rack of servers at each of its three branches. Approximate budget: AU$4000 each Requires: The units purchased must be rack mountable with 3000VA power ratings. Concerns: The most serious concern for the company is maximising system uptime in the event of a power failure. Staff need to be able to prepare for the possibility of a lengthy period without their equipment. Cost and ease of management are also considerations, as is the ability to scale up to meet future needs. Best solution: In terms of the main criterion, runtime, all the machines were reasonably close (see Runtime Testing). If the differences involved between them is a concern, then you'd best get some extra external battery packs or a larger UPS because you're sailing very close to the wind. Price wise, it's hard to beat MGE's Pulsar Extreme C. 
Editor's choice: Pulsar Extreme C
This article was first published in Technology & Business magazine. Click here for subscription information. About RMIT IT Test Labs
RMIT IT Test Labs is an independent testing institution based in Melbourne, Victoria, performing IT product testing for clients such as IBM, Coles-Myer, and a wide variety of government bodies. In the Labs' testing for T&B, they are in direct contact with the clients supplying products and the magazine is responsible for the full cost of the testing. The findings are the Labs' own -- only the specifications of the products to be tested are provided by the magazine. For more information on RMIT, please contact the Lab Manager, Steven Turvey.
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