?Green storage?: strategies for enhancing energy efficiency

Computer Technology Review,  Spring, 2007  by Bob Wambach

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Energy costs in the data center are rising at a dizzying rate. They already account for the second largest line item associated with datacenter operations and are predicted to rise to 50% of the overall IT budget in just a few years.

Steadily rising energy costs have been the norm for some time now, with customers paying more for power every year. Today, the average cost of utilities for a 100,000-square-foot data center is running at a staggering $5.9 million annually, and it?s getting worse. Even if an enterprise devotes this level of spend to energy every year, it runs the risk of running out of power eventually, especially if it?s powered via an older utility infrastructure: Gartner reports that by 2008, 50% of IT managers will not have enough power to run their data centers. Compounding this problem, data centers waste energy on inefficient server and storage infrastructures, with wastage calculations running as high as 60% in many environments. Yet in spite of these present and future challenges, the situation is not entirely bleak.

IT has already made inroads into controlling energy costs associated with servers. With ten million--and counting--servers installed in the U.S. alone, corralling runaway server costs has already resulted in significant energy savings. IT managers have focused their early energy efficiency efforts on consolidating and virtualizing servers, moving away from the common x86 server model with an average 24-hour utilization rate of 10% to 15% toward powerful new server technologies for which utilitization rates run 75% and higher. The savings have been dramatic: in data centers optimized for energy efficiency, cost savings gained by reducing the power footprint for cooling and electrical approach 80%. And the energy savings does not stop at the server itself: consolidation also reduces the number of power-grabbing switches, backup servers, and other server-related components.

Yet in spite of dramatic gains in server consolidation and energy savings, there remains a gaping hole in the enterprise data center: storage. IDC pegs raw storage growth now approaching a whopping 60% compounded annual growth rate. Storage is gobbling up power, and the same principles that govern server power savings should be applied to storage as well.

Storage: A World of Its Own

Historically, servers have consumed much more power than storage, but this trend has changed in recent years. Two factors have changed this dynamic:

  Server technology is on a very fast development path, so the same
  amount of server power consumption last year will deliver more
  processing power on this year?s server technology. Storage technology
  is limited by hard disk drives that have been evolving at a more
  measured pace, so the number of drives per server is growing.
  Increased business continuity requirements, which necessitate the
  replication of data to protect against system, site or even regional
  failures, and the growing trend to leverage a great variety of
  information for business operations are driving customers to store
  more data than they ever have before. And because of stringent
  compliance regulations such as Sarbanes Oxley, many organizations have
  decided that it is safer to retain all company information.

As a result, even though data centers may commonly cut 50% or more power consumption with server consolidation projects, without a corresponding effort on the storage side, data centers will continue to suffer from significant ? and unnecessary--energy demands.

Energy demands in the storage domain occur both in the server-to-storage data path and in storage-to-storage tiers. Energy management requires a comprehensive approach with end-to-end management from servers to primary storage to storage tiers.

Storage and Servers

Even now, the majority of storage utilized in many large computing environments is attached to small servers. There is a shortsighted but common IT purchasing practice that promotes the acquisition of another cheap server with additional disk drives when more storage is needed for an application. However, the reality is that each drive is only utilized 10-15% on average. Simple math demonstrates what a waste of energy and resources this practice translates into. Scaling out cheap servers is tempting at the outset because it is so easy to do, but it will bite back via poor management capabilities and energy drain in the long run. Instead of going with an energy-intensive and cumbersome direct-attached storage (DAS) model, plan purchases around optimized, networked storage.

Tiered Storage

Information lifecycle management and tiered storage strategies are critical to managing storage on many levels, and power consumption is an important factor. For background, a tier one array configured with 73 GB drives might deliver significantly more performance than a tier two array configured with 500 GB drives, but it also consumes a lot more energy per terabyte stored because it requires many more drives to achieve the same capacity.