Factors to consider when buying a UPS

Factors to consider when buying a UPS

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As you select a UPS, consider functionality and features as well as long-term durability. Resilience, management and monitoring, bypass control, and maintenance and output are the key components to compare for your organization's particular needs.

Resilience. A UPS is typically a reliable device, but it can become a single point of failure that affects multiple servers connected to it. If each server is virtualized and hosts multiple virtual machines (VMs), the potential for workload disruption can be enormous. So any evaluation of data center UPS systems should take resilience options Hp 398876-001 battery into account.

One option is to select a UPS that supports multiple power inputs, allowing two different sources to power the UPS unit. If one utility line fails, power from the other line can run the load and keep the UPS charged.

Another approach is to select UPS systems that Hp 396008-001 battery support parallel operation. Not only does this allow for greater runtime, but if other batteries in parallel fail, UPS power will still be available. This is termed +1 redundant because two UPS systems are running in parallel. If multiple UPS systems can be configured in parallel, it’s generally called an N+1 architecture, where N devices supply the required load and +1 ensures that load demands are met if one UPS should fail. For example, the Tripp Lite SU40KX UPS supports both 1+1 and N+1 configurations.

Still, experts recommend a careful assessment of UPS stability as load conditions change. “Particularly if you are installing a redundant UPS, step-function stability would be another important criterion to examine,” said Robert McFarlane, an analyst at Shen Milsom & Wilke, a technology consulting and design firm in New York. “When the entire load is suddenly thrown onto the remaining UPS, it has to reach stability very quickly.”

Many data center managers prefer to Hp 395789-001 battery use parallel operation to scale up UPS capacity. McFarlane advises against purchasing an oversized UPS to accommodate future growth, citing that this method is inefficient (if all of the UPS unit’s capacity isn‘t needed), can waste capital and is not environmentally friendly.

Many servers are built with redundant power supplies. Using a strategy sometimes called 2N redundancy can give you additional resilience if you connect each of the server’s redundant power supplies to a different UPS. Budget-conscious organizations may connect one supply directly to line power and a second supply to a UPS.

Management and monitoring. Don’t forget the Hp HSTNN-DB20 battery importance of UPS manageability. Although USB and RS-232 (serial port) connectivity may be suitable for small installations, data center UPS systems should include IP connectivity to allow remote management across an Ethernet LAN—the same mechanism that supports remote server, storage and other systems management in the data center. The HV Series from Controlled Power Co., for example, supplies three IP-type controllers offering a variety of communication features.

Good management tools allow you to monitor your equipment from anywhere and receive alerts if something goes wrong. “You should also be able to direct critical information to your [building management system],”McFarlane said.

Facilities personnel are also responsible for Hp Pavilion dv8000 battery
(Hp dv8000 battery) power distribution, which includes UPSes, so integrating the building management system wherever possible is important. If a UPS problem arises, the system will alert both IT and the facilities team.

An application or a Web/SNMP interface typically monitors and manages the UPS, and allows the administrator to track factors like UPS temperature, power, available runtime, current load (in kVA or watts) and battery condition. The admin should then be able to remotely control operations such as controlled shutdowns and restarts.

Experts note that the level of information and control that UPS management software allows can be a serious security flaw for careless organizations. “It should be possible to disable remote control of anything in the data center and just get operational readouts,” McFarlane said. “Anything you can access and control remotely could also be accessed and controlled by a hacker or disgruntled former employee.”

Bypass control capabilities. The choice of which Hp pavilion dv6000 battery
(Hp dv6000 battery) UPS unit works best for your data center must extend beyond basic design and transformer use. A bypass control capability that allows the UPS to be completely removed from the power-distribution system is a feature that’s often overlooked.

This may seem counterintuitive for an online UPS design, but the feature can prevent a defective UPS from causing a power outage that extends downtime. In addition, the ability to “bypass” a UPS allows field maintenance and repair without disruption to the load. For example, the 30 kVA APC Smart-UPS VT on page 8 is one system that supports automatic internal bypass.

Without such a bypass, McFarlane said, you could find yourself “in the embarrassing position of having to explain why utility power is still on, but your expensive UPS has become a roadblock between Hp 342661-001 battery [utility power] and your data center, causing everything to do a hard crash.”

Maintenance and output. Maintenance and repair are certainly major concerns for UPS deployments, particularly for batteries that eventually wear and fail. When shopping for a UPS, think about what will happen once its batteries die. For example, field-replaceable batteries allow technicians to easily upgrade or replace batteries (often with no tools). Selecting a UPS with hot-swappable batteries allows technicians to replace old or damaged batteries without having to take the entire UPS out of service first.

As UPS systems evolve and gain intelligence, they are getting more adept at Hp 345027-001 battery controlling how output power is delivered to the load. For example, a UPS with controlled output groups lets the UPS first shut down less-important loads such as print servers, allowing more runtime for important loads like a SQL Server.

Output groups also allow administrators to cycle power to one group to reboot a troublesome server without having to reboot everything attached to the UPS. Conversely, the UPS can use controlled output groups to sequence the startup of servers so that more important equipment starts first.

Another feature appearing in some Hp PP2182L battery UPS systems allows the unit to turn off power to a load that is in standby or otherwise “sleeping.” This feature might be useful in a virtual server environment where you can migrate active loads to fewer servers, and the UPS can shut down those idle servers to save even more power.