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Reliability in the Data Center
Keep the heart of the station beating strong
A room filled with computers obviously needs air conditioning. If you are in the process of building a new facility, you may not have all that much input on which units get chosen (aside from giving electrical consumption figures to your MEP engineer). However, due to the 24/7 nature of systems such as this, and your 24/7 need to know what is going on inside the data center, make sure you look at the BACnet and SNMP capabilities of any A/C units that are specified. BACnet is a communications protocol that allows devices such as A/C units to talk directly with BMS systems, and many manufacturers support it; take a look at this Web page for more specifics: bacnet.org/Gallery/index.html. Liebert, Trane, and Carrier are three well-known manufacturers on that list.
SNMP is the communications protocol that will allow you to keep track of what is going on via an SNMP manager. Just because a manufacturer supports BACnet doesn't mean that there is SNMP support. The way to find out is to take the specified manufacturer, then the model number of the LAN interface card that fits in it. Check its specifications then. All is not lost though if there is no support for SNMP; several companies make BACnet-to-SNMP converters. Control Solutions is one. Another is Chipkin.
Alternate power sources are also very important for the 24/7 operation of a data center. There are two types of power outages to be concerned with. First, the inevitable "momentary" that is just long enough to let power supplies sag -- but not long enough to bring on the emergency power. And, of course, those that are. The first is handled by a UPS -- and the second by an emergency power source. Let's talk about both of these.
UPSs have become important since more and more computers have shown up at the radio station because, as we all know, they don't like momentary power hits. There are a couple of considerations aside from the power handling capability:
■ Will there be a UPS per rack, or a large one that is the source for all racks?
■ Battery powered (the usual choice) or perhaps flywheel powered?
If you opt for a single, large UPS then, again, you'll be providing information to your MEP engineer about the load size (which pretty much is what it is, right?) and the length of time you want to be able to hold everything up -- in other words, how long the UPS can power the data center on its own. Clearly this is a budget issue -- not only in the cost to acquire the unit, but to install it, and to maintain it. Large capacity means lots of batteries and higher maintenance costs down the road. And don't forget to build-in extra capacity. We all know more computers get added as time goes on.
The other choice -- putting rack-mount UPSs in where they are necessary -- has its advantages and disadvantages as well. The primary advantage is expense. You buy and install a rack-mount UPS as needed. With one large UPS you focus your maintenance attention on it, of course -- but with smaller unit scattered about, you'll need to keep track of every individual unit. To me that is a disadvantage. As far as battery expense goes -- it's going to depend upon the size and number of batteries in a large UPS -- which will all get changed at once -- versus the cost dozens and dozens of smaller lead-acid cells.
You will find your job of maintaining UPSs is much easier if you always buy the network interface adaptor that comes with the unit. This will give you browser access -- so you can see what is going on from anywhere -- or perhaps even SNMP support, so that you can monitor the health of all the various units on a 24/7 basis. There are many manufacturers from which to choose when it comes to UPSs: Emerson (Liebert), APC, Toshiba, and Mitsubishi are some of the better known ones. For (relatively) small UPSs I'd like to bring one more brand to your attention -- Falcon Electric. The company specializes in double-conversion types -- in other words, ac to dc, then back to internal ac sine-wave generation. This type of online UPS eliminates power line transients very effectively -- especially compared to a unit that passes the ac through -- only switching to battery power as necessary.
- continued on page 5
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