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Know your underutilization

Before you can manage your growth, you have to know how much space you aren?t using.

Know your underutilization
Rick Cook

Before you can manage storage-system growth, you have to know how much of your systems are not being used. But that isn't as easy to figure out as you might think. This tip offers some basic guidelines for determining underutilization.

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However that is only part of the underutilization. In fact more than half of the storage capacity may be unused. "There are really two levels of underutilization, volume and dataset," explains Michael Spotts, corporate evangelist for StorageTek, a Louisville, CO maker of storage systems. Spotts says that most application administrators, especially database administrators, also keep excess capacity to allow for growth of their application. "The database administrator allocates excess space because you don't want to do a reorganization every few months," Spotts says. The result is that actual underutilization is often much higher than realized.

The first step in reducing underutilization is to know how much storage isn't being used. At the volume or LUN level this is fairly simple, Spotts says, because most operating systems and storage management software can produce reports on storage utilization. The dataset level is trickier, he says. "At the dataset level you're either going to have to have a DBMS tool or write code yourself," he says. Once storage administrators have an accurate picture of how much storage is not being used, they can begin to manage more effectively.

Additional Resources:
1. How can I achieve more efficient system utilization?
The hot button at IBM's recent storage and storage networking symposium was storage management. Every vendor talked about it. Every user wanted to know more about it, and a good portion of the education sessions were devoted to it. Softek, the storage arm of hardware maker Fujitsu, is one company that touted its upcoming product as the key to solving the storage management blues. In this exclusive searchStorage interview, Nick Tabellion, the company's chief technology officer and a 20-year veteran of the storage industry, gives his insight into the problem and hints to a possible solution.

2. Am I attaining better than 40 percent storage utilization?
Let's hope so; however, a recent study performed by Cahners In-Stat Group indicates you may very well not be. In this tip, Ruya Atac, senior director of Enterprises Markets for StorageNetworks, Inc. discusses how to better manage and test your storage hardware and software purchases.

3. Where can I find quantitative info to guide me in making storage decisions?
This user wants to create a matrix to evaluate different storage options. Our SAN expert Christopher Poelker offers some guidance as well as more than two dozen factors to consider.

4. Do SANs have an aggregate I/O rate at which point the performance is drastically reduced?
Great question. And our storage networking expert Marc Farley has the answer. See what he has to say about I/O consolidation and other issues surrounding network topology.

About the author: 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.

Storage utilization is a balancing act. Unused storage is wasted, but the system needs some reserve capacity to allow for growth. Typically storage administrators will try to keep 20 to 30 percent reserve.

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