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So, what can be done? Here are five possible actions that can be taken to help in generating some thought and prompting some possibilities to solve the problem:
- Add more capacity by adding more storage devices. Seems simple, right? This only works if the NAS system is capable of adding more devices either by plugging in more disk drives into an empty slots or installing another drawer of devices. This requires that the NAS system be physically capable -- meaning there are open slots for the space and cabling necessary for installation of another drawer of disks (that probably will have to come from the NAS vendor). These will require a configuration change and may involve some interruption of service (but not with all implementations). This requires an understanding as to whether this is possible or not with this particular product.
- If the NAS system is capable of being in some type of clustered arrangement, another node with associated capacity could be added. This is not available for all NAS systems and the installation and configuration requires some planning. This could provide some availability features, such as failover, depending on the vendor implementation. Also, this provides an opportunity to scale not only capacity but performance. Adding capacity alone may create a performance bottleneck, so the performance requirements need to be considered before just adding capacity.
- A second NAS system could be installed and then a NAS aggregator could be put in front of the NAS systems so that they appear to clients as a single NAS system. This requires the installation and configuration of both systems and will probably require an outage during the aggregator installation. This is an interesting approach in that once the aggregator (sometimes called network file virtualization) is installed, more NAS systems could be added without major impacts.
- A bigger (capacity-wise) NAS system could be installed and data moved from the NAS system that has run out of space. Some of these NAS systems provide the capability to "drain" the data from the other NAS system while providing client access. Maybe this isn't really adding capacity, but it is solving a capacity problem and may be the best choice in some circumstances. Those circumstances include:
- The inability to upgrade the NAS system.
- The NAS system reaching its projected end of useful life when maintenance costs become prohibitive.
- The NAS system is no longer being supported by the vendor.
- This is the most obvious way to add capacity to the NAS system: Manage your data. Surveys have shown that more than 60% of data is actually eligible for archiving, so that data could be moved to an archive device and that space can immediately be reclaimed. It is also incredibly useful to look at the data stored and get rid of what is useless. Do you really need all those mp3 files? How many copies of the same data are valuable? For many NAS systems, just enforcing quotas will make a big difference in the capacity available. So, maybe this isn't adding capacity to the NAS system. But, it might be the fastest and cheapest way to get more capacity.
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About the author: Randy Kerns is an independent storage consultant. In the past, he served as vice president of strategy and planning for storage at Sun Microsystems Inc., and covers storage and storage management software including SAN and NAS analysis.
This was first published in October 2006