Power struggle

Data centres worldwide are on a fault zone between two colliding forces. On one side, the geometric growth of data is generating ever-increasing demand for servers, storage and the infrastructure to support them. More data means more hardware, larger data centres and the requisite increase in power and cooling to sustain continuous operation. On the other side, the limited availability and increasing cost of energy worldwide is undermining the energy utilities’ ability to supply clean, reliable power. Industry forecasts now project that nearly all data centres internationally will not have sufficient power resources within 5 years, and many data centres are already power constrained due to utility limitations.

Given that modern enterprises and institutions all depend on information technology for their livelihoods, finding the means to align energy consumption to energy availability and simultaneously accommodate data growth are now critical components of a viable IT strategy. While there is no silver bullet to solve this problem, there is the now well-established concept of silver buckshot, or applying energy efficiency across myriad technologies to collectively reduce the external impact of energy consumption and solve the internal challenges of maintaining productive operations.

The Storage Networking Industry Association has formed the Green Storage Initiative (GSI) to help address this problem. In the US, data centres currently consume two percent of total energy production. While two percent may not seem to be a substantial number, it equates to billions of dollars of cost and is the equivalent of half a dozen 1000 megawatt power plants. Of the total data centre power draw, roughly half is due to cooling equipment and half to the complex of servers, storage and infrastructure required to support business applications. The SNIA GSI has thus taken up the silver buckshot of discovering more energy efficient means to run data centre storage operations while still accommodating the inevitable growth of storage data.

The SNIA GSI charter lists a multi-pronged approach for advancing energy efficient storage networking solutions, including advocacy, promotion of standard metrics, education, development of energy best practices and alliances with other industry energy organisations such as The Green Grid. Currently, over 20 SNIA members have joined the SNIA GSI as voting members.

A key requirement for customers is the ability to audit their current energy consumption and to take practical steps to minimize energy use. The task of developing metrics for measuring the energy efficiency of storage network elements is being performed by the SNIA Green Storage Technical Work Group (TWG). The SNIA GSI is supporting the work of the GS-TWG by implementing tests of industry metrics for storage networking products and promoting GS-TWG metrics for industry standardization.

Going green in the data centre has many facets, including reduction of overall power consumption, more efficient utilization of the power used, reduction of hardware via consolidation, aligning storage to data requirements and decreasing the total amount of storage required to meet data needs. Collectively, vendors and customers will need to implement comprehensive strategies that cooperatively integrate hardware, software and operational elements.

Compared to consumer products that may more readily lend themselves to energy-saving features (such as EPA Energy Star compliance), a data centre infrastructure poses considerable challenges in achieving energy efficiency. Business today is global and data centres must typically support non-stop operations. Data transactions demand immediate response times to meet both business and customer satisfaction requirements. Because continuous operation is essential for the viability of an enterprise, there are few idle elements in a storage network that could leverage, for example, low-power hibernation techniques typical of consumer electronics.

Data centres are inherently power-hungry. The challenge is to temper the energy appetite of data centre operations and maximise data transaction output per unit of energy consumed. Some advances have already been made on this front, as demonstrated by vendors who have proactively incorporated power efficiency into their product designs. In addition, new storage technologies such as server and storage virtualisation, information lifecycle management, storage compression and data de-duplication are enabling more efficient use of storage assets and overall reduction of the carbon footprint.

Given the sheer volume of file and application servers used by today’s enterprises, servers are a prime candidate for a green makeover. More efficient AC to DC conversion, reduced heat dissipation and more efficient use of CPU cycles by individual servers have a significant impact when multiplied by the thousands of servers typical of large data centres. By enabling multiple instances of operating systems and applications to be hosted on a single server hardware platform, server virtualisation promises to reduce the total amount of hardware and associated power consumption to service business applications. Blade server architecture likewise significantly reduces the hardware footprint required to support applications, and depending on the supplying vendor may have greater energy efficiency than rack-mount or stand-alone servers. The combination of concentrated blade servers and server virtualisation software can thus support more data transactions on less energy consuming real estate and help reduce the circumference of the data centre and its cooling requirements.

For the storage network infrastructure that ties servers to storage, the complex of switches and directors typical of large data centres represents another green challenge. Data sheet power ratings may vary from actual usage depending on how the storage network is designed and what layers of connectivity must be supported. The current trend in data centre consolidation is to eliminate more fabric elements by collapsing connectivity into larger port-count fabric directors in a tiered, core-edge design. In addition, auxiliary storage services for multi-protocol support, distance connectivity, high-speed inter-switch links, fabric-based storage virtualisation and data migration facilities are being integrated on more sophisticated director platforms. The larger chassis required to support port connectivity and advanced storage services should therefore be designed for optimum energy efficiency, particularly for enterprise data centres that deploy hundreds of directors supporting thousands of servers and storage devices.

For storage arrays, a number of options exist to minimize energy usage. Individual disks drives may be relatively cheap, but each spinning disk represents continuous power consumption. Typically, the faster the disk, the more power consumed. Mission-critical applications with high availability and high performance requirements may indeed need the very fastest disk drives and full mirroring (doubling the total number of disks) to sustain operations. The data generated by those applications, however, may age with declining business value. By combining information lifecycle management to track the value of data at any point in time with tiered classes of storage it is possible to migrate data from a higher energy usage asset to a lower one. A second tier array using lower speed SATA drives, for example, would be a more energy efficient repository for lower value data before the data finally retires to an even more efficient media such as tape. In addition, new technologies such as MAID (massive array of idle disks) provide on-demand access to disk data with the majority of drives in an array spun down until a data request is received.

Other green storage options attempt to reduce the total amount of storage required to house corporate data. While data growth has been a constant for all enterprises and institutions, a significant portion is due to redundant copies of data dispersed throughout the network. For file-oriented applications, in particular, identifying and eliminating redundant copies of files can dramatically reduce total storage requirements. Implementing a global name space, for example, can facilitate elimination of dispersed file silos and contain the tendency to replicate data as a convenience for local access. Likewise, data compression to disk and data de-duplication technologies can preserve data accessibility while reducing the amount of storage, disk drives and accompanying power usage required.

Data redundancy is also an inherent inefficiency for companies with geographically dispersed sites and remote offices. If every remote location has its own storage, green storage issues are multiplied across the corporate network. The current trend in remote storage consolidation is to centralise storage assets at an optimized central data centre and leverage WAN acceleration to service file access.

The former metric of cost per gigabyte of storage capacity was limited to hardware and operational costs. The green metric is kilowatt cost per gigabyte, or more appropriately, kilowatt cost per disk. Even spare drives in a typical storage cabinet are always on, always spinning, always drawing power and always dissipating heat. Implementing tiered storage, storage virtualisation, lifecycle management, data compression and de-duplication can help lower the carbon impact of a data centre and reduce overall costs.

In response to the rising cost of energy and its limited availability, some large enterprises are simply relocating to areas with lower energy costs. New data centres being built in the US along the Columbia River in Washington are taking advantage of the relatively lower cost of hydroelectric power compared to conventional coal or oil-based power generation. While this does save money and lessens the environmental impact vis-à-vis carbon-emitting power sources, there are still environmental issues concerning hydroelectric power and the storage infrastructure within the data centre still needs attention. Going green means that all aspects of IT operations including facilities, people and infrastructure must be re-examined to identify areas where greater power efficiencies can be achieved and around which proactive best practices can be established.

The SNIA encourages all storage networking vendors, channels, technologists and end users to actively participate in the SNIA GSI and help discover additional ways to minimize the impact of IT storage operations on power consumption. Given that adequate power for many data centres will simply not be available, we all have a vital interest in reducing our collective power requirements and make our technology do far more with far less environmental impact.

About the author

In addition to sitting on the SNIA board, Tom Clark is Principal Analyst and resident SAN evangelist for Brocade. A noted author and industry advocate of storage networking technology, he has held chair positions for SNIA customer initiatives and the SNIA Interoperability Committee. Clark has published numerous articles, white papers and books on storage networking.