Blade servers are self-contained servers embedded in dense, ultra-thin printed circuit boards (PCBs) called blades. A chassis called a razor houses the blades, which are usually proprietary and not interchangeable with another manufacturer’s devices. Blades increase the capacity of industry-standard data center racks because they require less room than other PCBs. Blade servers reduce computing costs by sharing important components such as power supplies, cooling fans, and network interfaces. Blade servers also require fewer cables, simplifying the work of system and network administrators.
Blade servers use several different types of central processing units (CPUs). Intel, Advanced Micro Devices (AMD), Motorola, and Sun Microsystems manufacture CPUs according to a variety of specifications. Blade servers also differ in terms of supported random access memory (RAM) and cache memory. The cache contains the data that is accessed most often by the CPU and memory. Cache memory accounts for a small amount of high-speed RAM and is the memory that the processor uses most often. The cache runs almost as quickly as the processor.
In terms of connectivity, blade servers use several types of Ethernet protocol over local area networks (LANs). 10Base-T uses twisted-pair cables to operate at 10 MB/s to a maximum length of 100 meters. These cables use RJ-45 connectors and broadband transmission, and are thinner and more flexible than the coaxial cables used with the 10Base-2 and 10Base-5 standards. 10Base-2 (Thinnet) uses 50-ohm coaxial cables to a maximum length of 185 meters. Like 10Base-T, Thinnet operates at 10 MB/s and uses baseband transmission. Fast Ethernet, a 100 MB/s Ethernet specification, includes two physical links between nodes: one for transmission and one for reception. Gigabit Ethernet is the standard for high-speed Ethernet.
Blade servers use several alternatives to Ethernet, including token ring, fiber channel, and fieldbus network protocols. Token ring technology is based on the use of a small frame, called a token, which circulates when all stations are idle. Fiber channel uses optical fibers to provide high-speed connections between computers and peripheral devices that operate at high bandwidths. The most prominent fiber channel standard, arbitrated loop (FC-AL), can support full-duplex data transfer rates of 100MBps. Fieldbus is a generic term that describes an all-digital communications network protocol used in industry as a Local Area Network (LAN) for factory / plant instrumentation and control devices. The network is a digital, bi-directional, multidrop, serial-bus, communications network used to link isolated field devices, such as controllers, transducers, actuators and sensors.
In large part, blade servers are deployed as front-end systems for web hosting, calendaring, portal services, directory services, and network management. These applications run effectively and affordably on single-processor systems such as blade servers.
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