A good test of a technology is, how long does it stay around? A great example is stereo sound. Introduced in 1931, it lived through the “quadraphonic revolution” of the seventies that some thought would surely replace it, and is now living through surround sound, which was also predicted as the death knell of simple stereo. People only have two ears — and stereo continues to live on.
An example in the computer world would be Storage Area Networks (SANs). Storage Area Networks (SANs) have long ago removed storage traffic from production networks and eased server processing times. They are now available to many companies that previously could not afford to implement them, thanks to simplification of hardware, software and installation. As technology does, SAN continues to be the target of innovation, with drives continuing to become faster and more efficient, and new technologies such as virtualization now being incorporated to make SANs even more capable.
One factor affects SAN the way it affects all hard-drive-based technologies, however: file fragmentation. No matter the speed and efficiency of the data being written to and read from a hard drive, if the data on that drive is fragmented, it’s going to automatically slow up the process. The more the fragmentation, the slower the transfer times to and from the disks within the SAN. The whole point of a SAN is to make drastic reductions in time and resources — and fragmentation can completely negate those reductions.
One of the vital performance-enhancing advancements in SAN technology is thin provisioning. But even this, if used without fragmentation also being addressed, not only loses performance but also wastes space. While the storage management system allocates space using thin provisioning, the file system may simply write data wherever it finds space. If data is written to a “high” logical cluster number (say, cluster 200), all clusters from zero to 200 are then allocated even if they are 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.
Like most crucial computer resources today, SANs must remain constantly up and running. The only way fragmentation can be properly addressed is if the solution operates automatically, requiring no scheduling and not interfering with running processes. The solution must be geared to a true enterprise-level operation.
Today, a majority of fragmentation can be totally prevented before it occurs — and this can happen invisibly, in the background. As SANs continue to advance, make sure your company fully and completely addresses the underlying fundamental of file fragmentation.
[awsbullet:storage area network o’reilly]