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The need to defragment NAS and the process you use to go do it varies depending on the solution purchased. The more advanced NAS solutions bought by medium to large scale enterprises have in-built utilities which, based on predetermined settings and algorithms, will defragment drives when tolerance thresholds are exceeded. Others rely on the operating system's defragmentation capability (if supported) or third party tools to minimise performance impacts on I/O due to fragmentation.
The impact of fragmentation will vary according to read and write patterns. If your environment typically sees random write followed by random read, the impact will be less than if there was a requirement for large sequential read and writes. To optimise performance a number of options are available, which are described below.
To defragment NAS volumes using the operating system's inbuilt capability relies on the administrator's interpretation of requirements, or pre-defined scheduling. Third party tools or application utilities can work with automated intelligence monitoring performance thresholds which initiate defragmentation based on diminished I/O performance.
All options can be scheduled to run during "quiet" times to minimise the impact of defragmentation on production activities. Third party tools and some utilities can be set to only run defragmentation processes using untapped resources, ensuring peak performance is maintained to service higher priority I/O requests. This provides the capability to defragment in real time, negating the requirement for fixed scheduling and long running defragmentation processes.
In summary, different NAS appliances offer differing capabilities for defragmentation and the impact the defragmentation process has on your appliance will be driven by how the specific solution tackles the problem.
More on NAS and the NAS defragmentation process
This was first published in July 2009