What is a SAN?


As computer networks expand and their user bases grow, the need for timely access to information grows with it. Information once accessed through a central file server is now being accessed by multiple servers, which are often running a variety of operating systems and applications. This sub-network of shared storage devices comprises a SAN. These servers share access to the storage devices (disks and tapes) where the data ultimately resides. The advantage of a SAN is that shared storage resources can be accessed directly by the server needing the data, thus reducing system response time, freeing up additional bandwidth, and improving overall network efficiency. (See Fig. 3)


Background of SAN


The last 25 years has seen a dramatic shift in computer network configurations. The highly centralized, mainframe-based computing mode (see Fig.1) has given way to the decentralized client/server design (see Fig. 2) commonly found in today's data centers. Taking a page from both configurations, the relatively new Storage Area Network (SAN) is essentially a hybrid of the two models. Technological advances like symmetric multi-process, fault-tolerant multi-processors with fail-over, and clustering govern and make an effective SAN possible.


SANs often consist of several types of servers running different operating systems. This enables users from a wide variety of platforms to access common storage information. But because of the inherent bandwidth considerations, not to mention corruption and security concerns, network performance cannot be maximized until resources are allocated.

What is Zoning?


Zoning is a logical separation of traffic between host and resources. By breaking up a network into zones, processing activity is distributed evenly across a network so that no single device is overwhelmed. This 'load balancing' is especially important for networks where it's difficult to predict the number of requests that will be issued to a server.


Similar to an O/S File System, zoning often employs directories and folders to organize and allot hard drive space. This is what ensures that each user (or group) has his or her own dedicated space reserved on the file server.

















Reasons to Zone a Network


Zoning enables servers to more efficiently run a network, yet there are many other advantages:

·         Data Integrity -- Many SANs contain more than one operating system. If left unchecked, servers with conflicting operating systems would be able to write to each other's native file system, inviting data corruption.

·         Security -- Employee salaries should not be universally accessed, but everyone should have access to a company activities calendar. Securing sensitive data is just smart business.

·         Shorter boot-up -- By narrowing the device discovery process to a particular zone, boot-up time is minimized.


So how does one go about zoning a SAN? Depending on a host of factors, including network size, company need, and a variety of storage devices, zoning can occur either at the target-level, or LUN-level.




 Next (Zoning Methods)


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