Introduction to System Area Networks
A system area network (SAN) is a high-performance, connection-oriented network that can link a cluster of computers. A SAN delivers high bandwidth (1 Gbps or greater) with low latency. A SAN is typically switched by hubs that support eight or more nodes. The cable lengths between nodes on a SAN range from a few meters to a few kilometers.
Unlike existing network technologies such as Ethernet and ATM, a SAN offers a reliable transport service; that is, a SAN guarantees to deliver uncorrupted data in the same order in which it was sent. Connection endpoints in a SAN are not required to use the TCP/IP protocol stack to transfer data unless traffic must be routed between subnets. SAN-local communication can use a native SAN transport, bypassing the TCP/IP protocol stack.
A SAN network interface controller (NIC), a transport driver for the SAN NIC, or a combination of both exposes a private transport interface. However, because most networking applications are written to use TCP/IP through Windows Sockets, they cannot use a SAN directly. The Windows Sockets Direct components shown in the following figure let these applications benefit from using a SAN transparently without requiring modification. Windows Sockets Direct is part of:
Microsoft Windows 2000 Datacenter Server
Microsoft Windows 2000 Advanced Server SP2
Microsoft Windows 2000 Server Appliance Kit SP2
Microsoft Windows Server 2003
The following figure shows the architecture required to support a SAN. The shaded areas represent components that a SAN NIC vendor supplies to enable using a SAN.
The following is a description of the components shown in this figure.