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What is a Storage Area Network?

SAN stands for storage area network. It is a network that has the purpose of providing block level data storage access and it designed to be able to cope with large transfers of data. The main purpose of a SAN is the transfer of data between the storage device and the computer. It allows devices like disk arrays or tape libraries to then be accessible to servers and display them as if they were locally attached to the computer. Having a SAN means that there is no limit to the amount of data that the server can access – usually this would be restricted by how many storage devices the individual server has attached to it.

With a SAN you can make use of speedy data transfers between the servers and the storage devices. SANs are often use for accessing data such as email servers, databases and file servers that see a high amount of activity. For example, data could be transferred from the server to storage, with the advantage being that the storage can be accessed by multiple servers at the same time. Alternatively, the SAN can allow for storage to storage transfer, which means that the data can be moved without the need for the server to get involved. This means that the server processor can be spared for other tasks.

So what are the other benefits of using a SAN? The fact that the storage is shared across the network means that it is simpler to control; there is no need to physically relocate storage devices as it can all be done through the SAN. This means there is more flexibility and also scalability. The fact that everything is centralized means it is much easier to manage. Another advantage is that servers can load from the SAN, which means that if a server is faulty its logical unit number can be reconfigured and the replacement server can then use it. Finally, a SAN is also great for disaster recovery. Having a good SAN infrastructure can help against component or software failures and human error. For example, a secondary storage array could be stored elsewhere, which means that the data can be replicated in case of disaster. Maintenance can also be performed on it without the need for any downtime, which stops disruption to the business.

It is important not to confuse SAN with network attached storage (NAS). A SAN will typically use fibre channel connection while a NAS uses Ethernet and TCP/IP. With a NAS, the system is grabbing a piece of an abstract file rather than a disk block like a SAN. Put simply, a NAS is an individual storage device that works with data files, while a SAN uses disk blocks on a local network across multiple devices. However, as technology progresses, some of the features that were once only available on either a SAN or NAS are now possible on the other. It can also be the case where a network set up could involve both solutions.

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