Enter the Blade Server
Blade servers are modular, single-board computers that are approximately the size of a network card. Using blade servers, the density of CPUs per rack is in the hundredsa far cry from the possible 40 processors that can fit in a standard 72-inch rack. This improvement provides for a massive increase in the deployable resource density. Each blade in a chassis is typically a self-contained server. Additional blade options can be installed to support fiber channel, gigabit Ethernet, hard disk, flash disk, PCI I/O expansion, and SCSI. Figure 1 illustrates a blade chassis with a number of server blades and some specialty blades.
Figure 1 Blade chassis and options.
The specialty blade options in Figure 1 can be used for a variety of purposes, such as the following:
Fiber channel for connecting to storage area networks (SANs)
Gigabit Ethernet for creating virtual LANs (VLANs)
PCI I/O for connecting to additional device types
Briefly, a storage area network (SAN) is a high-performance storage system in which units of storage are organized in a manner similar to that of a LAN. The storage is accessed by a front-end server, which connects to the disks. The server accesses the required storage and maps this to the requesting clients. As organizations deploy SANs, it will be important to allow access from blade systems.
Virtual LANs are a powerful technology for dividing and securing a Layer 2 network. This setup allows a network manager to divide a Layer 2 network such as Ethernet or ATM into individual broadcast domains. Traffic can then be directed into the broadcast domains as required; for instance, VLAN1 could be for internal LAN traffic, while VLAN2 is for Internet traffic. Typically, VLANs are constructed using special-purpose switches and routers. As for SAN, it's becoming important for blade systems to be able to interact with and join VLAN-based networks.