SAN brings many benefits to an enterprise. Stored data does not reside directly on a company’s servers, therefore business applications get the server power, and end users obtain the network capacity that would otherwise be utilized for storage. Administration is more flexible, because there is no need to shift storage cables and devices in order to move storage from one server to another. Servers can even be booted from the SAN itself, greatly shortening the time required to commission a new server.
There are numerous technologies employed to make SAN efficient, including RAID, I/O caching, snapshots and volume cloning, which have lead some to believe that SANs do not suffer the effects of file fragmentation. Fragmentation is the splitting of files into pieces (fragments) originally developed for the purpose of better utilizing disk space in direct attached storage devices.
The problem is that data is read and written by the operating system, and this is done on a logical, not a physical level. The OS’s file system, by its very nature, fragments files. While the data from the viewpoint of the NAS may appear efficiently arranged, from the viewpoint of the file system it is severely fragmented—and will be treated as such.
Fragmentation affects computer operations in numerous ways. Chief among them is performance; due to the fact that files must be written and read in thousands or even hundreds of thousands of fragments, performance is severely slowed down. In a fragmented environment, unexpected system hangs and even disk crashes are common. A heavy toll is taken on hardware, and disks can lose 50 percent or more of their expected lifespans due to all the extra work.
In past times, the solution to the fragmentation issue was a defragmenter. Because of many innovations in today’s computing environments—such as those used with SAN—a higher-level solution is needed. An optimization solution, which addresses a broader scope of issues than fragmentation only, is required.
Such a solution approaches numerous aspects of file read and write I/Os in addition to fragmentation. The majority of fragmentation itself is prevented before it even occurs, but also included is the intelligent ordering of files for faster access, along with other advanced technologies designed to automatically maximize system performance and reliability.
The best proof of fragmentation’s effects on SAN is through the testing of an optimization solution within an enterprise. Doing so, it will be clearly seen that fragmentation does indeed affect SAN operations—and they can only benefit from its elimination.