Balancing the Powerful Simplicity of SAN with Fragmentation Prevention

As with everything in computing, one of the primary goals developers have for storage area networks (SANs) is simplicity. SAN continues to advance with the advent of self-optimization, virtualization, storage provisioning and other benefits which make the technology more automatic. As SAN becomes more accessible and affordable, more companies are taking advantage of its many benefits.

The whole idea of a SAN, of course, is moving storage away from production servers, thereby freeing up resources for active company traffic. High-speed fiber channel networks make it possible for the switch to SAN to be invisible to the user, simply because speeds are similar to direct attachment of disks. Again, the goal is simplicity.

If file fragmentation is not addressed with an equally simple and powerful approach, this goal becomes less obtainable. All of this advanced technology must still read files from hard drives. Due to the splitting of files into thousands or tens of thousands of fragments, unnecessary complexities are introduced into the scheme. And access speed—another prime goal of a SAN—is nullified.

The various technologies being employed to assist SANs in being faster and more automatic each have their own unique susceptibility to fragmentation. For example, thin provisioning allows advance allocation of disk space. But at the same time, the file system may simply write data wherever space is to be found. If data is written to a “high” logical cluster number (say, cluster 200), all clusters from zero to 200 will be allocated even if not used. When data is added to an old file, new files are added or deleted, or an old file is expanded, the difference between file system disk allocation and storage system thin provisioning can contribute to fragmentation, over-allocation, and less efficient use of storage space.

Another example is virtual machines. At the very least, file I/Os are passed through a host and a guest system; file fragmentation wreaks havoc by adding multiple I/Os where there are already plenty extra.

Technology such as SAN requires an equally powerful—and simple—fragmentation solution. Following the trend of full automaticity, the most beneficial solution today is one which functions fully automatically, in the background, requiring no intervention from IT personnel. It is now even possible to prevent a majority of fragmentation before it occurs, putting its complex issues thoroughly in the past.

A SAN can now bring a robust resource saving storage solution to any site. As a companion, the fragmentation solution employed must be comparably robust—and simple.