Typical File Server Storage Utilization

cannot be easily changed to meet other needs. This also results in over allocation of storage to avoid having to allocated more storage later. All of this only adds to the problem

Steps you can take to reduce your storage power requirements include:

▲ Replace existing direct-attached storage with a storage network. Removing file servers reduces the amount of power required for storage, as well as increases flexibility. Instead of adding new servers, new disks can be added to increase storage.

Move to higher capacity drives. Higher capacity drives give you more bytes per watt.

Use SATA (Serial Advanced Technology Attachment) drives rather than Fibre Channel drives. While Fibre Channel drives have a higher data transfer rate, they use twice the power of a SATA drive per terabyte and many applications do not require the higher transfer rate. SATA drives also have a higher storage density than Fibre Channel drives.

Move rarely used data to near-line or off-line storage from on-line storage that is always powered.

Eliminate as much redundant data as possible. Use deduplication technology to reduce redundant data.

To measure the efficiency of your storage power system, determine the amount of power used per usable terabyte. This takes into account the utilization rate of your data storage and allows you to directly compare the storage energy efficiency among data centers or a single data center over time. While manufacturers will use watts per terabyte (W/TB) as a measure of power efficiency, it does not take into account how efficiently that storage is used. The formula for calculating this is:

watts per system

, 1 __ total terabytes watts per usable IB =---—-rate utilization


Another user of power in the data center is memory. The memory used in the vast majority of servers requires power to constantly refresh the contents of the memory, whether or not it is being read or written to. The most common type of memory is known as DRAM, or dynamic random access memory. This memory is configured in dual in-line memory modules (DIMMS)

and provides virtually instantaneous access to data. In addition, conventional hard drives are used for data that is not needed immediately, such as lower ranked search information. DRAM offers fast access to data, but consumes tremendous amounts of power.

Another problem with DRAM is the limited amount of this type of memory that can be used in a single server because of energy constraints at the DIMM level and the limited number of DIMM sockets within the server. Increases in the amount of data that needs to be in memory for quick access also requires servers to be added to meet this need, increasing the overall amount of power being used.

Several companies are working to reduce the amount of energy required to power server memory. Spansion, a spinoff of AMD and Fujitsu, produces memory based on flash technology that does not require power to retain its contents. It offers lower energy consumption as well as higher capacity, but is not as fast as traditional DRAM. Other companies, such as Micron Technology, are working on traditional DRAM that requires less voltage to maintain its contents and, therefore, uses less power and generates less heat. These alternative memory solutions use 15% to 75% less energy than traditional DRAM, potentially saving a significant amount of power in the data center.

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