Power and storage: the hidden cost of ownership - Storage Management

Computer Technology Review, Oct, 2003 by Chuck Larabie

Fred Moore, renowned storage engineer and author in the storage and high-tech industry, stated that the availability of electricity will become increasingly critical ("10 Challenges for the Storage Industry: How many do you think will be met in 2003?" Computer Technology News, January 2003). Moore also predicts that by 2010, over 50% of power consumed in the United States will be by computer technology. He is probably right. Already, today's data centers require well over 100 watts per square foot, or more than 10 times that of the average household.

Not only is electrical power generation being out-paced by demand, utility costs are one of the hidden cost burdens to any company. The power factor is rarely incorporated when equating the TCO (total cost of ownership) of storage. One of the biggest consumers of power within the computer technology industry is storage, and the little magnetic disk drive is one of the worst power hogs in the business. The magnetic disk drive is very similar to a honeybee. One is no problem. You can even have dozens, but when you reach hundreds or thousands then you have a swarm.

Thousands of spindles turning disc platters at 5400, 7200, 10000 and even 15000 RPM. All these hard drives living off electricity and, to make matters worse, they're generating heat.

The Cost of Electricity

Whether you live in Manhattan, Chicago, Atlanta or San Francisco, one thing is for sure: electricity is expensive! According to the latest Department of Energy study (2002), the average cost-per kilowatt-hour (KWh) in the U.S. was 6.93 cents. You're lucky if your data center is in Kentucky (4.1 cent/KWh), but no so lucky if your center is in Hawaii (13.9 cents). California and New York averaged 10 and 11 cents respectively. 1000 watts of power for mere pennies per hour may sound so miniscule, that you might consider it not worth factoring into the TCO equation; but as you will see, this miniscule amount grows painfully large.

For the sake of discussion, let's look at the fictitious company of Extensive Data Corporation (EDC) in the fictional city of Storageville, CA. According to the California Public Utilities Commission, the utility rates for Storageville could be anywhere from 6.5 cents to 18 cents per KWh. At first glance, EDC might consider the cost of powering their data storage solution to be relatively minor, and might even resolve fallaciously that they can afford a virtual farm of data storage solutions. However, one glance at how much power a large storage system would likely consume and how much that power would cost, may change management's decision.

Calculating the cost of energy usage using the published energy requirements of one of the industry's top selling enterprise storage solutions, a 100-terabyte (TB) configuration requires 40KWh. Using a median California rate of 10 cents per kilowatt, the formula is simple:

#KWh x Cost per Kilowatt = Power Cost/Hr Or 40KWh x .10 = $4.00 or $96.00 per day Or $35,040 per year

If the utility charges stay constant (and you know it will go higher) calculated over 5 years, the base electrical costs for this 100TB of disk storage would be $175,200.00. If you have applied business continuance disk mirrors, then double the amount to $350,400.

We're not done with the calculators just yet. There is one other factor that we failed to take into consideration; all electrical products produce heat. Heat is called BTUs (British Thermal Units) and for every watt of power consumed, 3.41 BTUs are created. As a result, the 100TBs of RAID noted above generate approximately 136,400 BTUs per hour. The more power used, the more heat is produced, which must be compensated with cooling to prevent the products from overheating. Air conditioning systems installed on top of buildings are used to introduce cool air into the computer room to keep the temperature constant. Unfortunately, air conditioning systems use power, too, and the age and efficiency of the air conditioning system will determine how much electricity and cost necessary to keep the above storage system cool. The efficiency of an air conditioner is based on the K-Factor. High efficiency units may consume as little as .33 BTU to cool 1 BTU of Heat. Older units may have a 1:1 power to cooling ratio. Therefore the next calculation looks like this:

#BTU/3.4/1000 x .33 x .10 = Cost Or 136400/3.4/1000 x .33 x .125 = $1.32 Or 31.68 per day Or $ 11,563 per year

Prorate this again over five years and your cooling costs grow to $57,815 (again, double this amount if running a mirror). Adding the cost of running the storage unit to the electrical cost of cooling the storage unit, the total cost of power usage over five years is $233,015 or $466,030 mirrored.

Remember the statewide power crisis in California of 2000-2001? Its genesis can be traced to four major events:

* An energy deregulation bill signed in 1996 by then California Governor Pete Wilson, opening California's electricity market to competition.

* Although the state's population increased by an average of 600,000 people per year, during the 12 years preceding the Davis Administration, no new major power plants were built in California.