Storage area networks (SANs) are just about essential to large enterprises and they're becoming increasingly popular in SMBs. In spite of their cost and complexity, a lot of SMBs are finding SANs make sense
File access is slowing down.
If your LAN can't keep up with the demands placed on the system, access to files slows. A SAN not only offloads the storage from the LAN, it also handles storage operations more quickly because SANs are optimized for storage.
Your collection of NAS devices is getting hard to manage.
Simple NAS boxes are a fast, easy and cheap way to expand your storage. However, they are designed as standalone devices and they don't scale well. If you get too many of them you'll find your storage is harder to manage. Some symptoms that they are getting too hard to manage would be if you're doing same management task 23 times on different NAS systems, and having to manually move files to different network-attached storage boxes to balance your load.
Your storage needs are growing faster than you anticipated.
Storage expands, but if your storage is expanding more quickly than you planned you need to look at something like a SAN to help bring the storage under control. Not only do SANs come with management tools to handle large amounts of storage, but the load balancing features in a SAN allow you to increase storage utilization.
Network congestion is affecting overall system performance.
The obvious impact of moving too many files over a network is that file access slows down. The less obvious result is that everything on the network, not just file access bogs down, or in worst case, the network becomes unstable.
Storage management is eating up more time.
As the number of storage devices on the LAN grows so does the time needed to manage them. In addition to managing the individual storage devices, you've got to coordinate them to balance loads, get the best utilization, tune for performance, etc. A SAN by definition gives you one central point to manage your storage, saving time and effort.
You're centralizing IT.
Re-architecting your IT efforts is the ideal time to consider moving to a storage area network. With IT consolidation, server and storage virtualization, etc., companies are redesigning their information architectures to reflect changes in business policies, take advantage of new technologies, cut costs and gain competitive advantages. Recentralizing the data structure is an ideal time to seriously consider moving to a storage are network. SANs are a natural fit with virtualized servers, virtualized storage and other modern storage techniques.
Your data backups are outgrowing the window.
A SAN stretches your backup window by speeding up the file transfers involved in backup. In fact, a well-designed storage area network can largely eliminate the backup window by allowing you to back up even when the LAN is in heavy use with little or not performance hit.
You've got lots of multi-megabyte files on your network.
Large files need a fast network, especially for jobs like video editing. It is no accident that video editing was one of the first places where SANs were used. You can tune your storage area network for the size of the files you have to handle to and from storage, leaving the LAN set up for the emails and other day-to-day uses.
You need your network to scale.
SANs are inherently far more scalable than nearly any other approach. You can start fairly small and add switches and storage arrays to let you expand a SAN far beyond anything a SMB is going to need. A well-designed SAN will scale to cover anything a SMB is likely to need.
You need to move a lot of data to a lot of different places quickly.
Multi-source, multi-destination topologies benefit from the switch-oriented architecture of SANs. Depending on how information flows in your business, you can either segment your system to keep the users topologically close to the servers that feed them, or you can structure your network to maximize access between servers and users over the entire network. And if you find your initial setup isn't optimal, you can redesign the network, usually without having to add equipment.
You're probably not displaying all these symptoms and if you're just displaying one of them, other, cheaper, remedies for your storage issues may apply. (For example, if file access is slowing down, the first step is to perform an analysis of file operations to see where the bottlenecks are and tune your file system in the light of what you find.) However, if you system is displaying several of these symptoms you should seriously considering purchasing a storage area network.
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About the author: Rick Cook specializes in writing about issues related to storage and storage management.
This was first published in June 2009