IBM HS20 blade server. Two bays for 2.5" SCSI hard drives can be noticed in the upper left area of the image.

Blade servers are self-contained computer servers, designed for high density. Whereas a standard rack-mount server can exist with (at least) a power cord and network cable, blade servers have many components removed for space, power and other considerations while still having all the functional components to be considered a computer. A blade enclosure provides services such as power, cooling, networking, various interconnects and management - though different blade providers have differing principles around what should and should not be included in the blade itself (and sometimes in the enclosure altogether). Together these form the blade system. Image File history File linksMetadata Download high resolution version (3072x2304, 2509 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Blade server Metadata This file contains additional information, probably added from the digital camera or scanner... Image File history File linksMetadata Download high resolution version (3072x2304, 2509 KB) Summary Licensing File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Blade server Metadata This file contains additional information, probably added from the digital camera or scanner... This article or section does not cite any references or sources. ... This article or section does not cite any references or sources. ... Equipment mounted in several 19-inch racks. ... The NASA Columbia Supercomputer. ...

In a standard server-rack configuration, 1U (one rack unit, 19" wide and 1.75" tall) is the minimum possible size of any equipment. The principal benefit of, and the reason behind the push towards, blade computing is that components are no longer restricted to these minimum size requirements. The most common computer rack form-factor being 42U high, this limits the number of discrete computer devices directly mounted in a rack to 42 components. Blades do not have this limitation; densities of 100 computers per rack and more are achievable with the current generation of blade systems. It has been suggested that this article or section be merged into 19-inch rack. ...

Server blade

In the purest definition of computing (a Turing machine, simplified here), a computer requires only; An artistic representation of a Turing Machine . ...

• memory to read input commands and data
• a processor to perform commands manipulating that data, and
• memory to store the results.

Today (contrast with the first general-purpose computer) these are implemented as electrical components requiring (DC) power, which produces heat. Other components such as hard drives, power supplies, storage and network connections, basic IO (such as Keyboard, Video and Mouse and serial) etc. only support the basic computing function, yet add bulk, heat and complexity, not to mention moving parts that are more prone to failure than solid-state components. This article or section does not cite any references or sources. ... A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ... In Computer Science, data is often distinguished from code, though both are represented in modern computers as binary strings. ... Die of an Intel 80486DX2 microprocessor (actual size: 12×6. ... Konrad Zuses Z3 was the first working programmable, fully automatic machine, whose attributes, with the addition of conditional branching, have often been the ones used as criteria in defining a computer. ... Direct current (DC or continuous current) is the continuous flow of electricity through a conductor such as a wire from high to low potential. ... A computer keyboard is a peripheral partially modeled after the typewriter keyboard. ... A computer display monitor, usually called simply a monitor when the meaning is clear from the context, is a piece of electrical equipment which displays viewable images generated by a computer without producing a permanent record. ... A contemporary computer mouse, with the most common standard features — two buttons and a scroll-wheel. ... A male DE-9 connector used for a serial port on a PC style computer. ...

In practice, these components are all required if the computer is to perform real-world work. In the blade paradigm, most of these functions are removed from the blade computer, being either provided by the blade enclosure (e.g. DC power supply), virtualised (e.g. iSCSI storage, remote console over IP) or discarded entirely (e.g. serial ports). The blade itself becomes vastly simpler, hence smaller and (in theory) cheaper to manufacture. A wall wart style variable DC power supply with its cover removed. ... . The initial letter is shown capitalized due to technical restrictions. ...

Blade enclosure

The enclosure (or chassis) performs many of the non-core computing services found in most computers. Non-blade computers require components that are bulky, hot and space-inefficient, and duplicated across many computers that may or may not be performing at capacity. By locating these services in one place and sharing them between the blade computers, the overall utilization is more efficient. The specifics of which services are provided and how vary by vendor.

Power

Computers operate over a range of DC voltages, yet power is delivered from utilities as AC, and at higher voltages than required within the computer. Converting this current requires power supply units (or PSUs). To ensure that the failure of one power source does not affect the operation of the computer, even entry-level servers have redundant power supplies, again adding to the bulk and heat output of the design. City lights viewed in a motion blurred exposure. ...

The blade enclosure's power supply provides a single power source for all blades within the enclosure. This single power source may be in the form of a power supply in the enclosure or a dedicated separate PSU supplying DC to multiple enclosures ^[1]. This setup not only reduces the number of PSUs required to provide a resilient power supply, but it also improves efficiency because it reduces the number of idle PSUs. In the event of a PSU failure the blade chassis throttles down individual blade server performance until it matches the available power. This is carried out in steps of 12.5% per CPU until power balance is achieved.

Cooling

During operation, electrical and mechanical components produce heat, which must be displaced to ensure the proper functioning of the components. In blade enclosures, as in most computing systems, heat is removed with fans.

A frequently underestimated problem when designing high-performance computer systems is the conflict between the amount of heat a system generates and the ability of its fans to remove the heat. The blade's shared power and cooling means that it does not generate as much heat as traditional servers. Newer blade enclosure designs feature high speed, adjustable fans and control logic that tune the cooling to the systems requirements.^[2]

Networking

Computers are increasingly being produced with high-speed, integrated network interfaces, and most are expandable to allow for the addition of connections that are faster, more resilient and run over different media (copper and fiber). These may require extra engineering effort in the design and manufacture of the blade, consume space in both the installation and capacity for installation (empty expansion slots) and hence more complexity. High-speed network topologies require expensive, high-speed integrated circuits and media, while most computers do not utilise all the bandwidth available. This article does not cite any references or sources. ...

The blade enclosure provides one or more network buses to which the blade will connect, and either presents these ports individually in a single location (versus one in each computer chassis), or aggregates them into fewer ports, reducing the cost of connecting the individual devices. These may be presented in the chassis itself, or in networking blades^[3]. IBM HS20 blade server. ...

Storage

While computers typically need hard-disks to store the operating system, application and data for the computer, these are not necessarily required locally. Many storage connection methods (e.g. FireWire, SATA, SCSI, DAS, Fibre Channel and iSCSI) are readily moved outside the server, though not all are used in enterprise-level installations. Implementing these connection interfaces within the computer presents similar challenges to the networking interfaces (indeed iSCSI runs over the network interface), and similarly these can be removed from the blade and presented individually or aggregated either on the chassis or through other blades. The 6-pin and 4-pin FireWire Connectors FireWire is Apple Inc. ... This article or section does not adequately cite its references or sources. ... This article or section does not cite any references or sources. ... Direct Attached Storage (DAS) refers to a digital storage system directly attached to a server or workstation, without a storage network in between. ... This article or section does not adequately cite its references or sources. ... . The initial letter is shown capitalized due to technical restrictions. ... IBM HS20 blade server. ...

The ability to boot the blade from a storage area network (SAN) allows for an entirely disk-free blade. This may have higher processor density or better reliability than systems having individual disks on each blade. In computing, a storage area network (SAN) is an architecture to attach remote computer storage devices such as disk array controllers, tape libraries and CD arrays to servers in such a way that to the operating system the devices appear as locally attached devices. ...

Other blades

Since the blade enclosure provides a standard method for delivering basic services to computer devices, these can be leveraged by other types of devices. Blades providing switching, routing, storage, SAN and fibre-channel access can be inserted into the enclosure to provide these services to all members of the enclosure.

Storage blades can also be used where additional local storage is desired.^{[4] [5]}

Uses

Blade servers are ideal for specific purposes such as web hosting and cluster computing. Individual blades are typically hot-swappable. As more processing power, memory and I/O bandwidth are added to blade servers, they are being used for larger and more diverse workloads. Web hosting is a service that provides individuals, organizations and users with online systems for storing information, images, video, or any content accessible via the Web. ... Linux Cluster at Purdue University A computer cluster is a group of locally connected computers that work together as a unit. ... Hot swapping is the ability to remove and replace components of a machine, usually a computer, while it is operating. ...

Although blade server technology in theory allows for open, cross-vendor solutions, at this stage of development of the technology, users find there are fewer problems when using blades, racks and blade management tools from the same vendor.

Eventual standardization of the technology might result in more choices for consumers; increasing numbers of third-party software vendors are now entering this growing field.

Blade servers are not, however, the answer to every computing problem. They may best be viewed as a form of productized server farm that borrows from mainframe packaging, cooling, and power supply technology. For large problems, server farms of blade servers are still necessary, and because of blade servers' high power density, can suffer even more acutely from the HVAC problems that affect large conventional server farms. Mainframe may refer to one of the following: Mainframe computer, large data processing systems Mainframe Entertainment, a Canadian computer animation and design company. ... All-air and air-water HVAC systems use air ducts, outlets, and inlets installed throughout their buildings. ...

History

Complete microcomputers were placed on cards and packaged in standard 19-inch racks in the 1970s soon after the introduction of 8-bit microprocessors. This architecture was used in the industrial process control industry as an alternative to minicomputer control systems. Programs were stored in EPROM on early models and were limited to a single function with a small realtime executive. Apple IIc Generally, a microcomputer is a computer with a microprocessor (µP) as its CPU. Another general characteristic of these computers is that they occupy physically small amounts of space. ... Equipment mounted in several 19-inch racks. ... Microprocessors, including an Intel 80486DX2 and an Intel 80386 A microprocessor (abbreviated as µP or uP) is an electronic computer central processing unit (CPU) made from miniaturized transistors and other circuit elements on a single semiconductor integrated circuit (IC) (aka microchip or just chip). ... Process control is an engineering discipline that deals with architectures, mechanisms, and algorithms for controlling the output of a specific process. ... Minicomputer (colloquially, mini) is a largely obsolete term for a class of multi-user computers which make up the middle range of the computing spectrum, in between the largest multi-user systems (traditionally, mainframe computers) and the smallest single-user systems (microcomputers or personal computers). ... EPROM. The small quartz window admits UV light during erasure. ...

The VMEBus architecture (ca. 1981) defined a computer interface which included implementation of a board-level computer that was installed in a chassis backplane with multiple slots for pluggable boards that provide I/O, memory, or additional computing. The PCI Industrial Computer Manufacturers Group PICMG developed a chassis/blade structure for the then emerging Peripheral Component Interconnect bus PCI which is called CompactPCI. Common among these chassis based computers was the fact that the entire chassis was a single system. While a chassis might include multiple computing elements to provide the desired level of performance and redundancy, there was always one board in charge, one master board coordinating the operation of the entire system. PICMG expanded the CompactPCI specification with the use of standard Ethernet connectivity between boards across the backplane. The PICMG 2.16 CompactPCI Packet Switching Backplane specification was adopted in Sept 2001 (PICMG specifications). This provided the first open architecture for a multi-server chassis. PICMG followed with the larger and more feature rich AdvancedTCA specification targeting the telecom industry's need for a high availability and dense computing platform with extended product life (10+ years). While AdvancedTCA system and board pricing is typically higher than blade servers, AdvancedTCA suppliers claim that low operating expenses and total cost of ownership can make AdvancedTCA-based solutions a cost effective alternative for many building blocks of the next generation telecom network. The PCI Industrial Computers Manufacturers Group (PICMG) is a consortium of over 450 companies that collaboratively develop open specifications for high performance telecommunications and industrial computing applications. ... This article or section does not cite its references or sources. ... This article or section does not cite its references or sources. ... Advanced Telecommunications Computing Architecture is the largest specification effort in PICMGs history, with more than 100 companies participating. ... A protocol and associated execution that ensures a certain relative degree of computing-system operational continuity in any downtime event. ...

The name blade server appeared when a card included the processor, memory, I/O and non-volatile program storage (flash memory or small hard disk(s)). This allowed a complete server, with its operating system and applications, to be packaged on a single card / board / blade. These blades could then operate independently within a common chassis, doing the work of multiple separate server boxes more efficiently. Less space consumption is the most obvious benefit of this packaging, but additional efficiency benefits have become clear in power, cooling, management, and networking due to the pooling or sharing of common infrastructure to supports the entire chassis, rather than providing each of these on a per server box basis. A USB flash drive. ... Typical hard drives of the mid-1990s. ...

(One opinion is that...) The architecture of blade servers is expected to move closer to mainframe architectures. Although current systems act as a cluster of independent computers, future systems may add resource virtualization and higher levels of integration with the operating system to increase reliability.

(An alternate opinion is that...) The architecture of blade servers will remain a set of separate servers within a common chassis. But, the chassis will be offered in a wider variety of sizes, providing different levels of aggregation and different cost points. On top of this independent server blade structure, management capabilities will be enhanced that allow operation of a collection of servers as a single compute resource pool. The administrators and users will not need to care which server an application is on, since the management software will automatically take care of allocating server (and I/O) resources to the application as needed. Over time, the individual servers will not need to be uniquely managed, but the overall roubustness of the data center will still benefit from the separation of individual servers, whose interconnect is provided by standard networking technology. This provides isolation at a very low level so that a fault in one piece of hardware impacts only that work executing on that specific hardware at that time. The broader management software can then recover the impacted work by initiating it on another server blade elsewhere in the data center.

Houston-based RLX Technologies, which consisted of mostly former Compaq Computer Corp employees, shipped the first blade server in 2001 ^[6]. RLX was acquired by Hewlett Packard (HP) in 2005.

According to research firm IDC, the major players in the blade market are tech giants HP and IBM. Other companies competing in this market are Supermicro, Hitachi, Sun Microsystems, Rackable (Hybrid Blade) and Verari Systems and Dell.

See also

• Server (computing)
• Comparing Servers

This article or section does not cite any references or sources. ...

References

1. ^ HP BladeSystem p-Class Infrastructure
2. ^ HP Thermal Logic technology
3. ^ HP Virtual Connect
4. ^ IBM BladeCenter HS21
5. ^ HP storage blade
6. ^ RLX blade server