Moderator: Peter Burris
Analyst: Nicholas Allen
The issue of energy consumption continues to grip the imagination of consumers, business executives and policy makers. IT storage professionals also must become aware of the relationship between faster, denser devices with higher performance levels and overall energy consumption and green implications. However, many IT professionals are uncertain about their ability to manage storage energy consumption, in part because of a built-in expectation at the application level of greater storage performance, higher capacities, and lower costs. They also see disk drives as component items chosen by array vendors and entering the data center as parts of larger systems, and therefore not under the storage administrator's direct control.
While these concerns are justified, IT professionals can make important choices in disk drive selection as part of their effort to reduce data center energy consumption. The two primary variables determining disk drive energy consumption are RPM and diameter. Energy consumption varies directly with disk RPM at approximately a 3:1 ratio (that is, energy consumption increases three times as fast as RPM increases) and directly with disk diameter at a 5:1 ratio. This means that reducing the size of disk drives from the present 3.5” to 2.5” can have a significant impact on drive energy consumption.
However, areal densities are not increasing fast enough to completely make up for the decrease in physical area of the smaller disks. Therefore, more platters must be added to provide the same storage capacity, which reduces the net power savings. At the same time, the smaller disks take up half the total space of the larger, older disks. The result is that in some situations the power, and heat, density of the resulting arrays can be 300% higher than those they replace.
We expect the transition from 3.5” to 2.5” disk drives will take place in high performance storage arrays in the next 12-18 months. This will probably lead to reintroduction of liquid cooling in some of these arrays and the data centers where they are housed. These heat and energy issues will probably allow 3.5” drives to sustain their market viability in tier 2 and 3 applications.
Meanwhile, users seeking to reduce the energy cost and carbon footprint of their storage systems might first want to investigate turning off spares. This, however, can cause conflicts with applications that presume striping, which spreads storage across all available drives. ITOs also should aggressively pursue tiered storage strategies that will allow them to deploy lower-performance drives with lower energy profiles for the fast-growing tier 2 and 3/bulk applications.
Energy concerns are likely to catalyze a call for the appointment of an individual with the authority and responsibility of bringing coherence to the ITO's overall strategy for minimizing the heat and energy challenges in the data centers, including new approaches to designing and deploying data center capacities.
Action Item: ITOs should not presume that storage is a given in their overall green strategies. While a green storage strategy is not synonymous with an overall green strategy, IT storage professionals can and should start taking steps to facilitate that overall green strategy in the business. These steps will require that storage administrators be very clear about the relationship between disk drives and energy when discussing green issues both with the rest of IT and the larger business. They should consider speedy adoption of technologies like tiered storage that will increase their degrees of freedom in choices on IT and energy.