Understanding How SAN And NAS Works
SAN architecture and terminology is getting confused as each product camp goes about praising the merits of their solutions. Storage is externalized from the server via Network Attached Storage or SAN Attached storage. NAS and SAS are very similar from an engineering standpoint.
Storage area network are fast becoming part of the IT. But the abundance of other storage management acronyms is making things a bit confusing. A SAN is a collection of networked storage devices that can automatically communicate with each other.
The key to understanding what makes a SAN is understanding that the goal is to divorce all users and network administrators from storage management. Storage, retrieval and file transfer are autimatically managed in a true SAN.
NAS is a disk array that connects directly to the messaging network via a LAN interface such as Ethernet using common communications protocols. It functions as a server in a client / server relationship that has a processor which process file I/O such as Server Message Block and Network File System.
A NAS system is connected to application servers via the network. But unlike a SAN , the NAS users can directly access stored data without server intervention. A SAN will automate management of storage system while NAS devices do not have this capability.
And when it comes to automated management in a SAN there is yet another definition floating around called hierarchical storage management. HSM is simply managing data movement from online to offline storage such as to tape devices.
Often referred to as the network behind the server , the SAN represents a new model that has evolved with the advent of multi host connected enterprise storage. A SAN bypasses traditonal network bottlenecks and support direct high speed data transfer in three different ways.
1 ) Server to Storage 2 ) Server to Server 3 ) Storage to storage
A SAN is an extended shared storage bus which can be interconnected using similar interconnected technologies as LAN or WAN , routers , switches and gateways. The three SAN components are the SAN interfaces , the SAN interconnects and the SAN fabric. SCSI , FC-AL , SSA , ESCOM are the common SAN interfaces. Extenders , Multiplexors , Hubs , Routers and Switches are the SAN interconnects.
SAN entail a large initial capital cost but in the long term benefits are significant. Recent studies suggest that half of all server attached storage goes unused becuase it cannot be shared. The trouble with technology myths is that technology keeps changing. Even if a SAN myth was true once but probably isn't today.
About the Author
Eddison Sherry had been working in Linux and Unix flavours for long years. He had been writing blogs and article on the Linux Storage , Linux Commands and Linux Server Administration. If you are working on Linux or Unix Server its best to have a look on his blogs at http://www.expertslogin.com/
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