Data Management

Best Practices for using Diskeeper®/V-locity® on Storage Area Networks (SANs)

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Executive Summary

As high-performing storage solutions based on block protocols (e.g., iSCSI, FC), SANs excel at optimizing block access. SANs work at a storage layer underneath the operating system's file system; usually NTFS when discussing Microsoft Windows?. That dictates that a SAN is unaware of "file" fragmentation and unable to solve this issue.

With file fragmentation causing the host operating system to generate additional unnecessary disk I/Os (more overhead on CPU and RAM), performance suffers. In most cases the randomness of I/O requests, due to fragmentation and concurrent data requests, results in the blocks that make up the file being physically scattered in uneven stripes across a SAN LUN/aggregate. This causes even greater degradation in performance.

Fortunately, there is an effective solution to NTFS file system fragmentation: a combination of preventing most fragmentation before it can happen and immediate defragmentation of any remaining. This white paper details how to achieve this automatically and significantly improve SAN performance without intruding into the SAN layer.

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