A storage area network (SAN) is any high-performance network whose primary purpose is to enable storage devices to communicate with computer systems and with each other.
the most interesting things about this definition are:
It doesn't say that a SAN's only purpose is communication between computers and storage. Many organizations operate perfectly viable SANs that carry occasional administrative and other application traffic.
It doesn't say that a SAN uses Fibre Channel or Ethernet or any other specific interconnect technology. A growing number of network technologies have architectural and physical properties that make them suitable for use in SANs.
It doesn't say what kind of storage devices are interconnected. Disk and tape drives, RAID subsystems, robotic libraries, and file servers are all being used productively in SAN environments today. One of the exciting aspects of SAN technology is that it is encouraging the development of new kinds of storage devices that provide new benefits to users. Some of these will undoubtedly fail in the market, but those that succeed will make lasting improvements in the way digital information is stored and processed.
It doesn't say that a SAN uses Fibre Channel or Ethernet or any other specific interconnect technology. A growing number of network technologies have architectural and physical properties that make them suitable for use in SANs.
It doesn't say what kind of storage devices are interconnected. Disk and tape drives, RAID subsystems, robotic libraries, and file servers are all being used productively in SAN environments today. One of the exciting aspects of SAN technology is that it is encouraging the development of new kinds of storage devices that provide new benefits to users. Some of these will undoubtedly fail in the market, but those that succeed will make lasting improvements in the way digital information is stored and processed.
REASON THAT MAKES SAN DIFERENT:
Anyone in the information technology field knows very well that computers are already connected to storage devices.
Universal Storage Connectivity
Computers are indeed connected to storage today, but are all of an installation's computers connected to all of its storage? That's the key point about SANs—they connect lots of computers to lots of storage devices, enabling the computers to negotiate device ownership among themselves and, ideally, to share data. If there is one defining characteristic of a SAN, it's universal connectivity of storage devices and computers.
Computers are indeed connected to storage today, but are all of an installation's computers connected to all of its storage? That's the key point about SANs—they connect lots of computers to lots of storage devices, enabling the computers to negotiate device ownership among themselves and, ideally, to share data. If there is one defining characteristic of a SAN, it's universal connectivity of storage devices and computers.
From this business-as-usual picture of client/server computing, it's immediately apparent that by deploying multiple servers, an organization automatically creates unconnected islands of information. Each island is accessible by one computer but not the others. If Computer B needs to use data that was produced by Computer A, that data has to be copied to Computer B.
There are several techniques for moving data between computers: backup, file transfer; and interprocess communication, to name a few. But the real issue is that the information services organization has to acquire and manage the extra resources required both to copy data from Computer A to Computer B and to store it at both sites. There's no business reason for this duplication of effort, other than that a computer needs data that was produced by another computer.
There's a more serious implication of an information processing strategy that relies on regular copying of data from computer to computer. Computers that receive data copies are often forced to work with data that is out of date simply because it's physically impossible to make copies in a timely fashion. Moreover, the extra operational complexity introduced by having to copy data between servers creates additional opportunity for costly errors.
There are several techniques for moving data between computers: backup, file transfer; and interprocess communication, to name a few. But the real issue is that the information services organization has to acquire and manage the extra resources required both to copy data from Computer A to Computer B and to store it at both sites. There's no business reason for this duplication of effort, other than that a computer needs data that was produced by another computer.
There's a more serious implication of an information processing strategy that relies on regular copying of data from computer to computer. Computers that receive data copies are often forced to work with data that is out of date simply because it's physically impossible to make copies in a timely fashion. Moreover, the extra operational complexity introduced by having to copy data between servers creates additional opportunity for costly errors.
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