What Are Blade Servers?
Blade servers are self-contained all-inclusive computer servers with a design optimized to minimize physical space. 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, which can hold multiple blade servers, provides services such as power, cooling, networking, various interconnects and management - though different blade providers have differing principles around what to include in the blade itself (and sometimes in the enclosure altogether). Together, blades and the blade enclosure form the blade system.
Blade servers function well for specific purposes such as web hosting and cluster computing. Individual blades are typically hot-swappable. As users add more processing power, memory and I/O bandwidth to blade servers, they deal with larger and more diverse workloads.
Although blade server technology in theory allows for open, cross-vendor solutions, users encounter fewer problems when using blades, racks and blade management tools all from the same vendor.
In a standard server-rack configuration, 1RU (one rack unit, 19" wide and 1.75" tall) defines the minimum possible size of any equipment. The principal benefit and justification of blade computing relate to lifting this restriction as to minimum size requirements. The most common computer rack form-factor is 42U high, which limits the number of discrete computer devices directly mountable in a rack to 42 components. Blades do not have this limitation; currently densities of up to 128 discrete servers per rack are achievable with the current generation of blade systems.
A computer server requires only the following to serve data:
- memory to read input commands and data
- a processor to perform commands manipulating that data
- backing storage to store the results
In practice, systems require all components if a 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), virtualized (e.g. iSCSI storage, remote console over IP) or discarded entirely (e.g. serial ports). The blade itself becomes vastly simpler, hence smaller and cheaper to manufacture.
The enclosure performs many of the non-core computing services found in most computers. Non-blade systems require bulky, hot and space-inefficient components, and may duplicate these across many computers that may or may not perform at capacity. By locating these services in one place and sharing them between the blade computers, the overall utilization becomes more efficient. The specifics of which services are provided and how vary by vendor.
The blade enclosure's power supply provides a single power source for all blades within the enclosure. This single power source may come as a power supply in the enclosure or as a dedicated separate PSU supplying DC to multiple enclosures. This setup reduces the number of PSUs required to provide a resilient power supply.
The popularity of blade servers, and their own appetite for power, has lead to an increase in the number of rack-mountable UPS units, including units targeted specifically towards blade servers (such as the BladeUPS).
During operation, electrical and mechanical components produce heat, which a system must displace to ensure the proper functioning of its components. Most blade enclosures, like most computing systems, remove heat by using fans.
The blade's shared power and cooling means that it does not generate as much heat as traditional servers.
At the same time, the increased density of blade-server configurations can still result in higher overall demands for cooling with racks populated at over 50% full. This is especially true with early-generation blades. In absolute terms, a fully populated rack of blade servers is likely to require more cooling capacity than a fully populated rack of standard 1U servers. This is because one can fit up to 128 blade servers in the same rack that will only hold 42 1U rack mount servers.
While computers typically use hard disks to store operating systems, applications and data, these are not necessarily required locally. Many storage connection methods (e.g. FireWire, SATA,E-SATA SCSI, DAS, Fibre Channel and iSCSI) are readily moved outside the server, though not all are used in enterprise-level installations.
The ability to boot the blade from a storage area network (SAN) allows for an entirely disk-free blade. This allows more board space to be devoted to extra memory or additional CPUs.
Since blade enclosures provide a standard method for delivering basic services to computer devices, other types of devices can also utilize blade enclosures. Blades providing switching, routing, storage, SAN and fibre-channel access can slot into the enclosure to provide these services to all members of the enclosure.
Systems administrators can use storage blades where a requirement exists for additional local storage
Blade servers do not, however, provide the answer to every computing problem. One can view them as a form of productized server-farm that borrows from mainframe packaging, cooling, and power-supply technology. Very large computing tasks may still require server farms of blade servers, and because of blade servers' high power density, can suffer even more acutely from the HVAC problems that affect large conventional server farms.
A blade enclosure, which can hold multiple blade servers, provides services such as power, cooling, networking, various interconnects and management - though different blade providers have differing principles around what to include in the blade itself (and sometimes in the enclosure altogether). Together, blades and the blade enclosure form the blade system.
Blade servers function well for specific purposes such as web hosting and cluster computing. Individual blades are typically hot-swappable. As users add more processing power, memory and I/O bandwidth to blade servers, they deal with larger and more diverse workloads.
Although blade server technology in theory allows for open, cross-vendor solutions, users encounter fewer problems when using blades, racks and blade management tools all from the same vendor.
In a standard server-rack configuration, 1RU (one rack unit, 19" wide and 1.75" tall) defines the minimum possible size of any equipment. The principal benefit and justification of blade computing relate to lifting this restriction as to minimum size requirements. The most common computer rack form-factor is 42U high, which limits the number of discrete computer devices directly mountable in a rack to 42 components. Blades do not have this limitation; currently densities of up to 128 discrete servers per rack are achievable with the current generation of blade systems.
A computer server requires only the following to serve data:
- memory to read input commands and data
- a processor to perform commands manipulating that data
- backing storage to store the results
In practice, systems require all components if a 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), virtualized (e.g. iSCSI storage, remote console over IP) or discarded entirely (e.g. serial ports). The blade itself becomes vastly simpler, hence smaller and cheaper to manufacture.
The enclosure performs many of the non-core computing services found in most computers. Non-blade systems require bulky, hot and space-inefficient components, and may duplicate these across many computers that may or may not perform at capacity. By locating these services in one place and sharing them between the blade computers, the overall utilization becomes more efficient. The specifics of which services are provided and how vary by vendor.
The blade enclosure's power supply provides a single power source for all blades within the enclosure. This single power source may come as a power supply in the enclosure or as a dedicated separate PSU supplying DC to multiple enclosures. This setup reduces the number of PSUs required to provide a resilient power supply.
The popularity of blade servers, and their own appetite for power, has lead to an increase in the number of rack-mountable UPS units, including units targeted specifically towards blade servers (such as the BladeUPS).
During operation, electrical and mechanical components produce heat, which a system must displace to ensure the proper functioning of its components. Most blade enclosures, like most computing systems, remove heat by using fans.
The blade's shared power and cooling means that it does not generate as much heat as traditional servers.
At the same time, the increased density of blade-server configurations can still result in higher overall demands for cooling with racks populated at over 50% full. This is especially true with early-generation blades. In absolute terms, a fully populated rack of blade servers is likely to require more cooling capacity than a fully populated rack of standard 1U servers. This is because one can fit up to 128 blade servers in the same rack that will only hold 42 1U rack mount servers.
While computers typically use hard disks to store operating systems, applications and data, these are not necessarily required locally. Many storage connection methods (e.g. FireWire, SATA,E-SATA SCSI, DAS, Fibre Channel and iSCSI) are readily moved outside the server, though not all are used in enterprise-level installations.
The ability to boot the blade from a storage area network (SAN) allows for an entirely disk-free blade. This allows more board space to be devoted to extra memory or additional CPUs.
Since blade enclosures provide a standard method for delivering basic services to computer devices, other types of devices can also utilize blade enclosures. Blades providing switching, routing, storage, SAN and fibre-channel access can slot into the enclosure to provide these services to all members of the enclosure.
Systems administrators can use storage blades where a requirement exists for additional local storage
Blade servers do not, however, provide the answer to every computing problem. One can view them as a form of productized server-farm that borrows from mainframe packaging, cooling, and power-supply technology. Very large computing tasks may still require server farms of blade servers, and because of blade servers' high power density, can suffer even more acutely from the HVAC problems that affect large conventional server farms.
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