SOURCE: Bruce Boyers Marketing Services

September 21, 2010 07:25 ET

Fragmentation Prevention and Crucial SAN Performance

BURBANK, CA--(Marketwire - September 21, 2010) -  Storage Area Networks (SANs) have meant a significant advance for enterprises and data centers. With data now moved off of a company's servers, both server power and network capacity are freed up for applications and users. With storage centralized, disks are easier to manage and maintain as well. Additionally, thanks to hardware, software and installation simplification, SANs are now available to many companies that previously could not afford to implement them. Further innovation is continuing to be released that assist SANs, with drives continuing to become faster and more efficient, and new technologies such as virtualization now being incorporated.

The entire object of a SAN is simplicity, supported by fiber channel networks that allow access speeds similar to those of disks that are directly attached. That simplicity can be fouled if SAN speed of response -- probably its most crucial element -- is slowed.

One factor above any other that slows SAN performance is file fragmentation. Undercutting the speed of the drive and the speed of the network technology is the state of the files on the disk. If they are fragmented, data being read and written will be considerably slower -- and all users and applications waiting for that data will be slowed as well. The entire purpose of a SAN is defeated.

There have been measures incorporated into SAN technology such as thin provisioning that are aimed squarely at performance enhancement. But even this innovation, if fragmentation is not also being addressed, loses performance and in addition wastes drive space. The storage management system allocates space using thin provisioning; at the same time, 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 will be 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.

Because it is a critical part of a company's computer operation, a SAN must remain constantly up and running. The ideal technology to apply to the fragmentation issue is one which prevents a majority of fragmentation from occurring, and does so fully automatically -- requiring no scheduling and never cutting across running processes.

A SAN can bring considerable power to a corporate network. Don't let it be brought down by file fragmentation.

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