Tools for capacity planning
Next to backup, capacity planning is perhaps the most important function in storage management because it is critical to making sure you don't run out of storage space. Capacity planning is complex and always somewhat cut-and-try. Fortunately, there are a number of tools and resources available to help with capacity planning.
Many storage products, especially NAS filers, have built-in utilities to track the use of storage. For example Procom Technology Inc. NetForce products keep track of the fill rate of the storage. Most storage management software tracks a variety of factors that influence capacity use, and many of them can predict when you will run short of storage based on how fast data is accumulating.
Although most administrators rely on standard rules of thumb or algorithms to know when to increase storage capacity, there are more elaborate methods available as well. In a frequently cited paper "Capacity planning with phased workloads," Borowsky et al. outline a method for keeping quality of service within bounds while handling a fairly general set of workloads. (http://citeseer.nj.nec.com/borowsky98capacity.html)
If your capacity planning is large or unusually complex, there are a number of consultants, such as Trilliant Group, which perform elaborate capacity audits and help construct plans to help prevent running low on storage.
Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last twenty years he has been a freelance writer specializing in storage and other computer issues.
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Scaling for E-Business: Technologies, Models, Performance, and Capacity Planning, 1/e
Author : Daniel A. Menasce and Virgilio A.F. Almeida
Publisher : Prentice Hall
Published : May 2000