Power Management in Data Centers

Rising electricity bills are causing a lot of sweat down the brows of data center admins across the globe. However, there are a lot of technologies available through which you can cut down on electricity bills. Read on...

Saturday, November 01, 2008

Akey element of every data center's physical infrastructure is power, which needs to be provided continuously to the equipment to ensure uninterrupted services. Unfortunately, this is easier said than done due to many reasons. One of them is the dynamic nature of data centers today.

Continuously, there's more equipment being added in data centers, which requires the requisite power to scale up accordingly. So obviously, if you've deployed a large, monolithic power management solution which can't be scaled with the requirement, then you're in for trouble. What's required is a modular power distribution and backup system, which can scale up with the
requirements.

Modular power units however, are not sufficient to cope up with the other key trends taking shape in data centers. For instance, power density per rack is also increasing in data centers thanks to the use of blade servers. Besides raising the power requirements, denser racks also lead to greater heat dissipation, thereby stretching the cooling system. The cooling system in turn also requires better power management to continuously do its work. So once again, it indirectly boils down to efficient power management and provisioning.

Another key trend that's related to data centers is IT infrastructure consolidation. Increasingly, organizations are preferring a centralized IT infrastructure over a distributed one. This improves the manageability, reduces costs, and improves uptime of the IT infrastructure. At the same time however, it requires better power management, because you're in a way putting all your eggs in one basket. Power failure could have a drastic impact on your organization's business.

All these trends have nearly doubled the energy consumption of data centers over the past few years. In fact, as a thumb rule, half of the total energy consumed in a data center is by the IT equipment alone. Unlike other equipment, IT equipment requires cleaner power and better monitoring becaue it's more prone to failure. So a combination of these factors is forcing IT departments globally to monitor data center power consumption and find ways of increasing energy efficiency.

In this article, we'll not talk about the backup solutions like UPSes that can be used in data centers for cleaner power and backup. Enough has been written about them by us as well as other media in the past. It would suffice to say that you need a scalable UPS system, which can easily grow with your IT requirements. So in this article, we'll focus on other aspects of power monitoring and management, which starts from choosing the right IT equipment itself, and then moves towards implementing solutions that can monitor and manage the power distribution to them. So let's start with the equipment.

Choice of IT equipment
Most IT vendors today are harping about providing energy efficient hardware, whether it's servers, storage, networking, or security. So before you can work out a proper power management strategy for your data center, you need to study the power consumption patterns of your existing equipment. Work out a strategy to gradually phase out all energy efficient equipment and replace with energy efficient ones. For instance, multi-core processors have caused a revolutoin in the server space, by adding more compute capability within the same form factor. You no longer need to invest in a bigger server box if you want more power. So if you haven't already, you need to work out a strategy for replacing existing servers in your data center with multi-core ones. Next, work out similar strategies for other equipment, e.g. moving to Network Attached or centralized storage over direct storage, to get better power consumption per Terabyte.

Using power saving technologies comes next. Server virtualization fits the bill just fine, as it allows you to improve the utilization of your existing servers, thereby reducing the need to purchase more boxes.

Once you've optimized the power consumption of the equipment in your data center, you're ready to monitor its power usage.

Using power management software
With so much IT equipment, it becomes essential to monitor the power being provided to them. Here you could go for direct or network attached power monitoring solutions. It would keep track of peak and idle load on servers. When the server is not in use, it could reduce the power supplied to it and vice versa.

Moreover, today, you can get software that let's an administrator set different power mgmt policies. You can also use software to keep track of energy being utilized by different equipment and plan a solution to minimize consumption.

Remote power management
Administrators can implement different hardware solutions to remotely manage the power of equipment in the data center. Servers can be remotely switched on/off or restarted. These solutions also provide you with the choice to restrict power to any device.

Smart load shedding
Certain power management hardware equipment have embedded smart load shedding features. Using this feature, non-essential equipment can be turned off when not in use. Such a feature is quite useful in situations when mains supply is not available. Turning off non-essential equipment would then improve the back-up time of a UPS.

Three-phase power
Implementing 3-phase 208 V power supply helps consolidate power needs and it is also simpler to implement and maintain as it uses fewer circuits as compared to single phase power supply. This results in overall reduction of power distribution units required to power the equipment and increase the available amperage for each server rack.

DC power distribution systems
Such a system helps reduce power consumption as conversion from AC to DC occurs only once at the main input to the building. The DC is fed directly to the servers and it also keeps the battery charged.

DC-powered servers don't have power supplies built-in but these are provisioned for elsewhere in the infrastructure. Using DC supply does away with the need for extra conversion. But this technology is suitable only for large data centers and there are not too many experienced people out there to handle such systems.

Designing an efficient system
The common design problems that lead to reduction in efficiency are:
1. Power distribution units and transformers operating well below their full load capacities.
2. Air conditioners for heating and cooling being used at the same place.
3. Tampering with the throttle valves of cooling pumps considerably reduces their efficiency.

The solution to these problems is to create a well-structured/tested design that places each of the equipment in the right order.

Employing effective cooling solutions
Cooling systems consume a considerable amount of the total energy consumed. Therefore effective cooling solutions should be used so that there's no wastage of power. Row oriented cooling has higher efficiency for high density. Shorter air paths require less fan power. An effective floor layout plays an important role in increasing the efficiency of cooling solutions.

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