Cooling and temperature control are becoming increasingly important in data centers, with organizations switching to high density servers for optimization of technologies such as virtualization. A little focus on the small details can lead to dramatic savings in data center power usage. A few things to watch out for are:
Temperature is the denominator of paramount importance to data center power management. Normal cooling or a computer room air conditioner (CRAC) are not sufficient for high density servers (blade servers). Data centers require a high degree of accuracy in temperature control.
There are standard norms as to what the inlet and outlet temperatures set by PUE should be. The temperature of the inlet at the front of the rack needs to be 21 degrees Celsius, with the maximum variation allowed being 1 degree from the norm. The outlet can be up to 31 or 32 degrees Celsius. The delta temperature (difference between inlet and outlet) should be 10 degrees.
Comfort ACs or even CRAC do not have the tolerance level of precision cooling, which can really help in optimizing data center power management, given the escalating number of blade servers generating more and more heat. Stress is being laid more on precision cooling now, as it is efficient in handling the massive heat loads generated by IT infrastructure.
For ideal data center power management, humidity should be around 50%, give or take 5%. In coastal areas humidity can go up to 70-80%, and in the rainy season it can go up to 90%. High humidity levels cause condensation, while the dryness from low humidity creates electrostatic discharges. If the temperature is very high, there is frequent booting of systems, which is not acceptable on mission-critical sites.
Earlier, data centers were built for a life span of 10-12 years. If you see the advancements in technology, earlier there were pizza boxes or 1U servers, and a rack was 42U (able to stack up to 42 servers in a single rack). These are each independent servers with fans, CD-ROMs, etc.
With blade servers, you have the 7U form factor, using vertical blades. The heat density keeps increasing. A 1U pizza box server consumes about 200 watts, while a 14-blade 7U server will consume about 3.5 kilowatts. The heat density has gone up almost ten times. One solution is to consolidate servers to the maximum. Thus, even if the heat density goes up on blade servers, server optimization and space savings will lead to data center power savings.
Types of used electric power
Power is a function of load, and the type (DC or AC) you are using affects data center power management. The kind of load and applications you have, will determine the type of power to use. Both DC and AC have their own pros and cons. The usage scenario varies from organization to organization.
The first thing to check is whether your organization will be upgrading the data center in the course of time. If so, then you need to have scalable power for successful data center power management. Power outages should not lead to any downtime in the UPS. One must make sure that the power supply is scalable along with being reliable. This can be achieved through adaptive architecture. One should make sure that the UPS has inbuilt transformers. Reliability gets compromised without it.
About the author: Pratik Chube is country general manager - product management & marketing at Emerson Network Power (India) Pvt. Ltd. He is responsible for all the product lines including power solutions, cooling solutions, racks & enclosures, monitoring solutions, and DC power, at Emerson. He is an expert on Energy Logic.
(As told to Jasmine Desai)