Disk drives are getting bigger, performance acceleration technologies abound, and capacity optimization tools are everywhere. All of these factors are affecting the perceived and actual cost of storage systems. As the way storage purchases are made continues to change, one thing is clear the cost per raw gigabyte of storage capacity has become a poor metric when purchasing performance-based storage systems, according to InfoStor contributor and IDC analyst, Noemi Greyzdorf.
Traditional purchasing decisions made on a dollar-per-raw-gigabyte basis may lead buyers to spending more than they presume simply because they are only buying capacity without consideration for other necessary attributes. These attributes include reliability, security, efficiency, performance, and manageability. When buying a storage system, consider the following:
The cost per raw gigabyte is a poor metric when purchasing a system to support performance-driven applications. It is imperative that the organization understands what applications will be hosted on the storage array and what their performance and capacity requirements will be over time. Having an understanding of the environment ahead of time will make the soliciting and evaluation of options simpler.
Performance acceleration technologies may have a direct impact on the ability of the storage system to deliver higher level of IOPS or throughput. Technologies such as compression or deduplication may have a similar impact on capacity and its utilization. The benefits must be viewed in light of any additional costs associated with deploying them and the actual results that can be expected based on the actual applications and data to be used.
Advantages of acceleration and capacity optimization technologies may come at a cost in complexity that translates to a storage system's manageability. Added complexity or reduction in manageability of the system over time may lead to unexpected costs in people, time, productivity, and competitiveness.
The storage industry has been trending along Moore's predicted line of growth with HDD capacity increasing and the cost per gigabyte decreasing. Since 2000, the average HDD capacity growth has been 36% while the cost per gigabyte has been declining at an average of 34.6%. During the same period, the typical seek time has only improved 5% to 10%. And HDDs still come in 5.4K, 7.2K, 10K, or 15K RPM versions. The result are drives that have increased in density from 18GB, 36GB, and 73GB drives at a maximum of 15K RPM in 2000 to 600GB 15K RPM drives in 2009. Managers often are forced into array layouts that waste capacity in order to spread the I/O over multiple spindles.
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