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64-400: The IBM 2145 SAN Volume Controller (SVC) is an inline virtualization or "gateway" device. It logically sits between hosts and storage arrays, presenting itself to hosts as the storage provider (target) and presenting itself to storage arrays as one big host. SVC is physically attached to one or several SAN fabrics. The virtualization approach allows for non-disruptive replacements of any part in

128-553: A road case approved by the Air Transport Association of America (ATA), sometimes also referred to as a flight case . Road cases typically have plywood sides laminated with polyvinyl chloride (PVC), extruded aluminum edges, steel corners, handles, and latches. Larger cases typically have wheels for easy transport. Road case racks come in different heights based on the 1U standard and different depths. Non-isolated cases simply mount 19-inch mounting posts inside

192-498: A 1.5U server or devices that are just 22.5 or 15 cm in width, allowing for 2 or 3 such devices to be installed side by side, but these are much less common. The height of a rack can vary from a few inches, such as in a broadcast console, to a floor-mounted rack whose interior is 45 rack units (200.2 centimetres or 78.82 inches) high. 42U is a common configuration. Many wall-mounted enclosures for industrial equipment use 19-inch racks. Some telecommunications and networking equipment

256-485: A 19-inch rack. With the prevalence of 23-inch racks in the Telecoms industry, the same practice is also common, but with equipment having 19-inch and 23-inch brackets available, enabling them to be mounted in existing racks. A key structural weakness of front-mounted support is the bending stress placed on the mounting brackets of the equipment, and the rack itself. As a result, 4-post racks have become common, featuring

320-465: A 2U, 19-inch rack mount enclosure. 1 Gbit/s iSCSI connectivity is standard, with options for 16 Gbit/s FC and 10 Gbit/s iSCSI/FCoE connectivity. It holds up to 24 2.5" SAS drives and supports the attachment of up to 20 Storwize V7000 expansion enclosures. IBM Storwize V7000 Gen 2+ is an updated Storwize V7000 Gen 2 with a newer CPU, doubled cache memory and faster FC options, integrated compression acceleration, and additional scalability with

384-951: A control enclosure and up to 10 standard expansion enclosures or 4 high-density expansion enclosures. It can scale up to 392 disks and 12.04 PB raw internal capacity. Storwize V5000 consists of one to two control enclosures and up to 12 expansion enclosures, for a maximum of 18 enclosures altogether. It can scale up to 480 disks and 960 TB raw internal capacity. Hardware details: Storwize V3700 consists of one control enclosure and up to 4 expansion enclosures. It can scale up to 240 2.5" disks or 120 3.5" disks and 480 TB raw internal capacity. Hardware details: Storwize V3700 also offers management and interoperability features from previous Storwize systems, include simple management capabilities, virtualization of internal storage and thin provisioning for improved storage utilization and one-way data migration to easily move data onto Storwize V3700. An entry-level SAN Volume Controller configuration contains

448-593: A control enclosure and up to 10 standard expansion enclosures or 4 high-density expansion enclosures. It can scale up to 392 disks and 12.04 PB raw internal capacity. Storwize V5030 consists of a control enclosure and up to 20 standard expansion enclosures or 8 high-density expansion enclosures. It can scale up to 760 disks and 23.34 PB raw internal capacity. Storwize V5020 consists of a control enclosure and up to 10 standard expansion enclosures or 4 high-density expansion enclosures. It can scale up to 392 disks and 12.04 PB raw internal capacity. Storwize V5010 consists of

512-572: A control enclosure and up to 20 standard expansion enclosures or 8 high-density expansion enclosures. It supports NVMe and FC-NVMe (NVMe-oF) on 16 Gbit/s, 32 Gbit/s adapters, and iSCSI/iWARP/RoCE ( iSCSI Extensions for RDMA ) on 25GbE adapters. It can scale up to 760 disks and 23.34 PB raw internal capacity. Hardware details: Storwize V5030E consists of a control enclosure and up to 20 standard expansion enclosures or 8 high-density expansion enclosures. It can scale up to 760 disks and 23.34 PB raw internal capacity. Storwize V5010E consists of

576-412: A cubic meter. Newer server rack cabinets come with adjustable mounting rails allowing the user to place the rails at a shorter depth if needed. There are a multitude of specialty server racks including soundproof server racks, air-conditioned server racks, NEMA-rated, seismic-rated, open frame, narrow, and even miniature 19-inch racks for smaller applications. Cabinets are generally sized to be no wider than

640-978: A gap of 17.75 inches (450.85 mm), giving an overall rack width of 19 inches (482.60 mm). The posts have holes in them at regular intervals, with both posts matching, so that each hole is part of a horizontal pair with a center-to-center distance of 18.312 inches (465.12 mm). The holes in the posts are arranged vertically in repeating sets of three, with center-to-center separations of 0.5 inches (12.70 mm), 0.625 inches (15.88 mm), 0.625 inches (15.88 mm). The hole pattern thus repeats every 1.75 inches (44.45 mm). Holes so arranged can either be tapped (usually 10-32 UNF thread, or, less often, 6mm metric ) or have square holes for cage nuts . Racks are vertically divided into regions, 44.45 millimetres (1.75 in) in height. Each region has three complete hole pairs on each side. The holes are centered at 6.35 millimetres (0.25 in), 22.25 millimetres (0.88 in), and 38.15 millimetres (1.50 in) from

704-641: A minimum of 2 and a maximum of 8 nodes, and linear scalability. Nodes are rack -mounted appliances derived from IBM System x servers, protected by redundant power supplies and integrated batteries. Earlier models featured external battery-backed power supplies. Each node has Fibre Channel ports simultaneously used for incoming, outgoing, and intracluster data traffic. Hosts may also be attached via FCoE and iSCSI Gbit Ethernet ports. Intracluster communication includes maintaining read/write cache integrity, sharing status information, and forwarding reads and writes to any port. These ports must be zoned together. Write cache

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768-474: A mirrored pair of rear mounting posts. Since the spacing between the front and rear mounting posts may differ between rack vendors and/or the configuration of the rack (some racks may incorporate front and rear rails that may be moved forwards and backward, e.g. APC SX-range racks), it is common for equipment that features 4-post mounting brackets to have an adjustable rear bracket. Servers and deep pieces of equipment are often mounted using rails that are bolted to

832-491: A rack is typically described as rack-mount , rack-mount instrument , a rack-mounted system , a rack-mount chassis , subrack , rack cabinet , rack-mountable , or occasionally simply shelf . The height of the electronic modules is also standardized as multiples of 1.75 inches (44.45 mm) or one rack unit or U (less commonly RU). The industry-standard rack cabinet is 42U tall; however, many data centers have racks taller than this. The term relay rack appeared first in

896-494: A rotary-molded polyethylene outer shell are a lower-cost alternative to the more durable ATA-approved case. These cases are marketed to musicians and entertainers for equipment not subject to frequent transportation and rough handling. The polyethylene shell is not fiberglass reinforced and is not rigid. The shape of small cases is maintained by the rack rails and the cover seal extrusions alone. Larger cases are further reinforced with additional plywood or sheet metal. The outer shell

960-546: A wider folded strip arranged around the corner of the rack. The posts are usually made of steel of around 2 mm thickness (the official standard recommends a minimum of 1.9 mm), or of slightly thicker aluminum . Racks, especially two-post racks, are often secured to the floor or adjacent building structure so as not to fall over. This is usually required by local building codes in seismic zones . According to Telcordia Technologies Generic Requirements document GR-63-CORE, during an earthquake, telecommunications equipment

1024-435: Is h = 1.75 n − 0.031 for calculating in inches, and h = 44.45 n − 0.794 for calculating in millimeters. This gap allows a bit of room above and below an installed piece of equipment so it may be removed without binding on the adjacent equipment. Originally, the mounting holes were tapped with a particular screw thread. When rack rails are too thin to tap, rivet nuts or other threaded inserts can be used, and when

1088-401: Is industrial power, control, and automation hardware . Typically, a piece of equipment being installed has a front panel height 1 ⁄ 32 inch (0.031 in; 0.79 mm) less than the allotted number of Us. Thus, a 1U rackmount computer is not 1.750 inches (44.5 mm) tall but is 1.719 inches (43.7 mm) tall. If n is number of rack units, the ideal formula for panel height

1152-413: Is a large number of computers in a single rack, it is impractical for each one to have its own separate keyboard, mouse, and monitor. Instead, a KVM switch or LOM software is used to share a single keyboard/video/mouse set amongst many different computers. Since the mounting hole arrangement is vertically symmetric, it is possible to mount rack-mountable equipment upside-down. However, not all equipment

1216-562: Is a standardized frame or enclosure for mounting multiple electronic equipment modules. Each module has a front panel that is 19 inches (482.6 mm) wide. The 19 inch dimension includes the edges or ears that protrude from each side of the equipment, allowing the module to be fastened to the rack frame with screws or bolts. Common uses include computer servers , telecommunications equipment and networking hardware , audiovisual production gear, professional audio equipment, and scientific equipment . Equipment designed to be placed in

1280-509: Is a tendency for 4-post racks to be 600 mm (23.62 in) or 800 mm (31.50 in) wide, and for them to be 600 mm (23.62 in), 800 mm (31.50 in) or 1,010 mm (39.76 in) deep. This of course varies by manufacturer, the design of the rack and its purpose, but through common constraining factors (such as raised-floor tile dimensions), these dimensions have become quite common. The extra width and depth enables cabling to be routed with ease (also helping to maintain

1344-621: Is available in a narrower 10-inch format with the same unit height as a standard 19-inch rack. Frames for holding rotary-dial telephone equipment such as step-by-step telephone switches were generally 11 feet 6 inches (3.51 m) high. A series of studies led to the adoption of frames 7 feet (2.1 m) high, with modular widths in multiples of 1 foot 1 inch (0.33 m)—most often 2 feet 2 inches (0.66 m) wide. IBM Storwize V7000 IBM Storwize systems were virtualizing RAID computer data storage systems with raw storage capacities up to 32 PB . Storwize

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1408-471: Is based on the same software as IBM SAN Volume Controller (SVC). Formerly Storwize was an independent data storage organisation. Сollateral lines: The Storwize family offers several members: Each of the above family members run software that is based on a common source codebase, although each has a type specific downloadable package. In Feb 2020 the Storwize V5000 and V5100 are replaced by

1472-411: Is frequently embossed in a self-mating pattern to combat the tendency for stacked cases to deform slightly creating a slope that encourages the upper case to slide off. The cases typically use extruded aluminum bands at the ends of the body with tongue-and-groove mating to like bands for the covers. End covers are typically secured with either a simple draw latch or a rotary cam butterfly latch, named for

1536-435: Is mounted via rails (or slides). A pair of rails is mounted directly onto the rack, and the equipment then slides into the rack along the rails, which support it. When in place, the equipment may also then be bolted to the rack. The rails may also be able to fully support the equipment in a position where it has been slid clear of the rack; this is useful for inspection or maintenance of equipment which will then be slid back into

1600-529: Is protected by mirroring within a pair of SVC nodes, called I/O group . Virtualized resources (= storage volumes presented to hosts) are distributed across I/O groups to improve performance. Volumes can also be moved nondisruptively between I/O groups, e.g., when new node pairs are added or older technology is removed. Node pairs are always active, meaning both members accept simultaneous writes for each volume. In addition, all other cluster nodes accept and forward read and write requests which are internally handled by

1664-641: Is still used in legacy ILEC / CLEC facilities. Nineteen-inch racks in two-post or four-post form hold most equipment in enterprise data centers , ISP facilities, and professionally designed corporate server rooms , although hyperscale computing typically use wider racks. They allow for dense hardware configurations without occupying excessive floor space or requiring shelving. Nineteen-inch racks are also often used to house professional audio and video equipment, including amplifiers , effects units , interfaces, headphone amplifiers, and even small-scale audio mixers. A third common use for rack-mounted equipment

1728-409: Is subjected to motions that can over-stress equipment framework, circuit boards, and connectors. The amount of motion and resulting stress depends on the structural characteristics of the building and framework in which the equipment is contained and the severity of the earthquake. Seismic racks rated according to GR-63 , NEBS Requirements: Physical Protection, are available, with Zone 4 representing

1792-400: Is suitable for this type of mounting. For instance, most optical disc players will not work upside-down because the driving motor mechanism does not grip the disc. 19-inch server racks can vary in quality. A standard 19-inch server rack cabinet is typically 42u in height, 600 millimetres (24 in) wide, and 36 inches (914.40 mm) deep. This comprises a volume of 974 L, or just under

1856-691: The IBM Storwize V7000 , the first member of the Storwize family . Storwize uses the SAN Volume Controller code base with internal storage to provide a mid-price storage subsystem. The IBM Storwize V5000, V3700 and V3500 are shrunk compatible models with less cache/CPU/adapters and a reduced set of features. The IBM FlashSystem V9000 leverages the SVC firmware integrated with IBM FlashSystem solid-state drawers. In 2015, IBM re-badged

1920-608: The 4 node cluster and 380,489.30 with the 6 node cluster, records that stood until October 2011. Release 6.2 of the SVC held the Storage Performance Council (SPC) world record for SPC-1 performance benchmarks, returning over 500K (520,043.99) IOPS (I/Os per second) using 8 SVC nodes and Storwize V7000 as the backend disk. There was no faster storage subsystem benchmarked by the SPC at that time (January 2012). The full results and executive summaries can be reviewed at

1984-602: The FlashSystem 5000 and 5100 respectively; and the FlashSystem 900 and Storwize V7000 are replaced by the FlashSystem 7200. According to the official availability dates and the days the systems are removed from marketing you can determine the following availability to purchase shown in light green. The graphics only contains the IBM storage systems starting with 'V', .i.e. V3700, V5000, V5010(E), V5020, V5030(E), V5100 and V7000. These systems vary even beyond their names, therefore

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2048-472: The SPC website referenced above. Release 7.x provides multiple enhancements including support for additional CPUs, cache and adapters. The streamlined cache operates at 100μs fall-through latency and 60 μs cache-hit latency, enabling SVC as a front-end to IBM FlashSystem solid-state storage without significant performance penalty. (See also: FlashSystem V9000). There are some optional features, separately licensed e.g. per TB: On 7 October 2010, IBM announced

2112-579: The SVC held the Storage Performance Council (SPC) world record for SPC-1 performance benchmarks, returning nearly 275K (274,997.58) IOPS . There was no faster storage subsystem benchmarked by the SPC at that time (October 2008). The SPC-2 benchmark also returned a world leading measurement of over 7 GB/s throughput. Release 5.1 achieved new records with a 4 node and 6 node cluster benchmark with DS8700 as backed storage device. SVC broke its own record of 274,997.58 SPC-1 IOPS in March 2010, with 315,043.59 for

2176-499: The appropriate I/O group. Path or board failures are compensated by non-disruptive failover within each I/O group, or optionally across dispersed I/O groups. Hosts must have multipath drivers installed, such as IBM Subsystem Device Driver (SDD) or standard MPIO drivers. SVC is based on COMmodity PArts Storage System ( Compass ) architecture, developed at the IBM Almaden Research Center . The majority of

2240-515: The attachment of up to 20 Storwize V7000 expansion enclosures. IBM Storwize V7000 next-generation models offer increased performance and connectivity, integrated compression acceleration, and additional scalability with the following features: Software Details: Storwize V7000 consists of one to four control enclosures and up to 36 expansion enclosures, for a maximum of 40 enclosures altogether. It can scale up to 960 disks and 1.44PB raw internal capacity. Hardware details: Storwize V5100 consists of

2304-664: The case. To protect equipment from shock and vibration road rack cases use an inner and outer case. These cases can be isolated by thick layers of foam or may use spring-loaded shock mounting. Touring musicians, theatrical productions and sound and light companies use road case racks. In 1965, a durable fiber-reinforced plastic 19-inch rackmount case was patented by ECS Composites and became widely used in military and commercial applications for electronic deployment and operation. Rackmount cases are also constructed of thermo-stamped composite, carbon fiber , and DuPont 's Kevlar for military and commercial uses. Portable rack cases using

2368-602: The fans. However, some rack equipment has been designed to make fan replacement easy, using quick-change fan trays that can be accessed without removing the cabling or the device from the rack, and in some cases without turning off the device so that operation is uninterrupted during replacement. The formal standards for a 19-inch (482.6 mm) rack are available from the following: A rack's mounting fixture consists of two parallel metal strips (also referred to as posts or panel mounts ) standing vertically. The posts are each 0.625 inches (15.88 mm) wide, and are separated by

2432-480: The following features: In addition, other Storwize systems offer the following features (some of them may require licenses): In addition, the Storwize V7000 Unified offered the following features: Most Storwize systems are intended for certain environments and provide several features, that are not licensed by default. There are several types of licenses that depend on the chosen model and

2496-405: The following features: Software Details: The IBM Storwize V7000 SFF Control Enclosure Model 524, announced 6 May 2014, features two node canisters and up to 128 GiB cache (system total) in a 2U, 19-inch rack mount enclosure. 1 Gbit/s iSCSI connectivity is standard, with options for 8 Gbit/s FC and 10 Gbit/s iSCSI/FCoE connectivity. It holds up to 24 2.5" SAS drives and supports

2560-594: The front and exhaust on the rear. This prevents circular airflows where hot exhaust air is recirculated through an adjacent device and causes overheating. Although open-frame racks are the least expensive, they also expose air-cooled equipment to dust, lint, and other environmental contamination. An enclosed sealed cabinet with forced air fans permits air filtration to protect equipment from dust. Large server rooms will often group rack cabinets together so that racks on both sides of an aisle are either front-facing or rear-facing, which simplifies cooling by supplying cool air to

2624-423: The front and rear posts (as above, it is common for such rails to have an adjustable depth), allowing the equipment to be supported by four posts, while also enabling it to be easily installed and removed. Although there is no standard for the depth of equipment, nor specifying the outer width and depth of the rack enclosure itself (incorporating the structure, doors and panels that contain the mounting rails), there

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2688-413: The front of the racks and collecting hot air from the rear of the racks. These aisles may themselves be enclosed into a cold air containment tunnel so that cooling air does not travel to other parts of the building where it is not needed or mixes with hot air, making it less efficient. Raised or false floor cooling in server rooms can serve a similar purpose; they permit cooling airflow to equipment through

2752-607: The graphics also contains IBM type and model. All the displayed systems can still get regular service at the end of the timeline (beginning of 2020). For the IBM SAN Volume Controller's timeline see there. Storwize V7000 provides a very similar architecture to SVC, using the RAID code from the DS8000 to provide internal managed disks and SSD code from the DS8000 for tiered storage . All Storwize systems offer

2816-485: The minimum bend radius for fiber and copper cables) and deeper equipment to be utilized. A common feature in IT racks is mounting positions for zero-U accessories, such as power distribution units (PDUs) and vertical cable managers and ducts, that utilize the space between the rear rails and the side of the rack enclosure. The strength required of the mounting posts means they are invariably not merely flat strips but actually

2880-465: The most demanding environment. GR-3108 , Generic Requirements for Network Equipment in the Outside Plant (OSP), specifies the usable opening of seismic-compliant 19-inch racks. Heavy equipment or equipment that is commonly accessed for servicing, for which attaching or detaching at all four corners simultaneously would pose a problem, is often not mounted directly onto the rack but instead

2944-653: The particular class of equipment to be mounted is known in advance, some of the holes can be omitted from the mounting rails. Threaded mounting holes in racks where the equipment is frequently changed are problematic because the threads can be damaged or the mounting screws can break off; both problems render the mounting hole unusable. Tapping large numbers of holes that may never be used is expensive; nonetheless, tapped-hole racks are still in use, generally for hardware that rarely changes. Examples include telephone exchanges, network cabling panels, broadcast studios and some government and military applications. The tapped-hole rack

3008-523: The posts and allow the rack to be securely attached to the floor and/or roof for seismic safety. Equipment can be mounted either close to its center of gravity (to minimize load on its front panel), or via the equipment's front panel holes. The Relay Racks name comes from early two-post racks which housed telephone relay and switching equipment. Two-post racks are most often used for telecommunication installations. 19-inch equipment that needs to be moved often or protected from harsh treatment can be housed in

3072-418: The rack. Some rack slides even include a tilt mechanism allowing easy access to the top or bottom of rack-mounted equipment when it is fully extended from the rack. Slides or rails for computers and other data processing equipment such as disk arrays or routers often need to be purchased directly from the equipment manufacturer, as there is no standardization on such equipment's thickness (measurement from

3136-401: The rapid growth of the toll network, the engineering department of AT&T undertook a systematic redesign, resulting in a family of modular factory-assembled panels all "designed to mount on vertical supports spaced 19 1 ⁄ 2 inches between centers. The height of the different panels will vary,... but... in all cases to be a whole multiple of 1 + 3 ⁄ 4 inches." By 1934, it

3200-424: The shape of the twist handle. There is no standard for airflow and cooling of rack-mounted equipment. A variety of airflow patterns can be found, including front intakes and rear exhausts, as well as side intakes and exhausts. Low-wattage devices may not employ active cooling, but use only passive thermal radiation and convection to dissipate heat. For rack-mounted computer servers, devices generally intake air on

3264-407: The side of the rack to the equipment) or means for mounting to the rail. A rails kit may include a cable management arm (CMA), which folds the cables attached to the server and allows them to expand neatly when the server is slid out, without being disconnected. Computer servers designed for rack-mounting can include a number of extra features to make the server easy to use in the rack: When there

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3328-698: The software has been developed at the IBM Hursley Labs in the UK. The different SAN Volume Controller models were available for purchase shortly after the mentioned announcement day. The light green bars show the period of time when each model could be ordered, while the light blue bars show how long the standard service was continued after withdrawal from marketing. The displayed information is current in August 2019. There are differences in service conditions between 2145 and 2147, but not in hardware. Release 4.3 of

3392-461: The square-hole rack. Square-hole racks allow boltless mounting, such that the rack-mount equipment only needs to insert through and hook down into the lip of the square hole. Installation and removal of hardware in a square-hole rack is very easy and boltless, where the weight of the equipment and small retention clips are all that is necessary to hold the equipment in place. Older equipment meant for round-hole or tapped-hole racks can still be used, with

3456-618: The standard 24-inch-wide (610 mm) floor tiles used in most data centers. Racks carrying telecom equipment like routers and switches often have extra width to accommodate the many cables on the sides. Four-post racks allow for mounting rails to support the equipment at the front and rear. These racks may be open in construction without sides or doors or may be enclosed by front and/or rear doors, side panels, and tops. Most data centers use four-post racks. Two-post racks provide two vertical posts. These posts are typically heavy gauge metal or extruded aluminum. A top bar and wide foot connect

3520-515: The storage infrastructure, including the SVC devices themselves. It also aims at simplifying compatibility requirements in strongly heterogeneous server and storage landscapes. All advanced functions are therefore implemented in the virtualization layer, which allows switching storage array vendors without impact. Finally, spreading an SVC installation across two or more sites ( stretched clustering ) enables basic disaster protection paired with continuous availability. SVC nodes are always clustered, with

3584-2071: The subject of the license: There are some limitations for each model and each licensed internal code. These can be read on IBMs web pages. Here are examples for V7000, the V5000 series, and IBM SAN Volume Controller . In addition, there are more contributors to a working environment. IBM provides this in an interactive interoperabitlity matrix called IBM System Storage Interoperation Center (SSIC) . As of November 2016, available Storwize media sizes include 2.5" flash SSDs with up to 15.36 TB capacity and 3.5" Nearline-HDDs with up to 10 TB capacity, available for Storwize 5000, 7000 and SAN Volume Controller native attach. IBM Storwize Easy Tier will automatically manage and continually optimize data placement in mixed pools of nearline disks / standard disks / read-intensive Flash and enterprise-grade Flash SSDs, including from virtualized devices. The Storwize family hardware consists of control enclosures and expansion enclosures, connected with wide SAS cables (Four lanes of 6 Gbit /s or 12 Gbit/s). Each enclosure houses 2.5" or 3.5" drives. The control enclosure contains two independent control units (node canisters) based on SAN Volume Controller technology, which are clustered via an internal network. Each enclosure also includes two power supply units (PSUs). Eight available enclosure models: The IBM Storwize V7000 SFF Enclosure Model 724, announced November 6, 2018, supports NVMe and FC-NVMe (NVMe/FC) on 16 or 32 Gbit/s adapters, and iSER ( iSCSI Extensions for RDMA ) or iSCSI on 25GbE adapters. The Control Enclosure holds 24 2.5" NVMe flash drives or 24 2.5" NVMe FlashCore modules (FlashCore modules contain IBM MicroLatency technology with built-in hardware compression and encryption). Software Details: The IBM Storwize V7000 SFF Control Enclosure Model 624, announced 23 August 2016, features two node canisters and up to 256 GiB cache (system total) in

3648-472: The technology that is mounted within it has changed considerably and the set of fields to which racks are applied has greatly expanded. The 19-inch (482.6 mm) standard rack arrangement is widely used throughout the telecommunications , computing , audio , video , entertainment and other industries, though the Western Electric 23-inch standard , with holes on 1-inch (25.4 mm) centers,

3712-556: The top or bottom of the region. Such a region is commonly known as a U , for unit , RU for rack unit or, in German, HE , for Höheneinheit . Heights within racks are measured by this unit. Rack-mountable equipment is usually designed to occupy some integer number of U. For example, an oscilloscope might be 4U high. Rack-mountable computers and servers are mostly between 1U and 4U high. A blade server enclosure might require 10U. Occasionally, one may see fractional U devices such as

3776-400: The underfloor space to the underside of enclosed rack cabinets. A difficulty with forced air fan cooling in rack equipment is that fans can fail due to age or dust. The fans themselves can be difficult to replace. In the case of network equipment, it may be necessary to unplug 50 or more cables from the device, remove the device from the rack, and then disassemble the device chassis to replace

3840-428: The use of cage nuts made for square-hole racks. Rack-mountable equipment is traditionally mounted by bolting or clipping its front panel to the rack. Within the IT industry, it is common for network/communications equipment to have multiple mounting positions, including tabletop and wall mounting, so rack-mountable equipment will often feature L-brackets that must be screwed or bolted to the equipment prior to mounting in

3904-455: The virtualization functionality as Spectrum Virtualize , in order to align it with the IBM software-defined storage naming conventions and to highlight the interoperability aspect. The Actifio Protection and Availability Storage (PAS) appliance includes elements of SVC code to achieve wide interoperability. The PAS platform spans backup, disaster recovery, and business continuity among other functions. 19-inch rack A 19-inch rack

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3968-638: The world of telephony . By 1911, the term was also being used in railroad signaling . There is little evidence that the dimensions of these early racks were standardized. The 19-inch rack format with rack-units of 1.75 inches (44.45 mm) was established as a standard by AT&T around 1922 in order to reduce the space required for repeater and termination equipment in a telephone company central office . The earliest repeaters from 1914 were installed in ad hoc fashion on shelves, in wooden boxes and cabinets. Once serial production started, they were built into custom-made racks, one per repeater. But in light of

4032-474: Was an established standard with holes tapped for 12-24 screws with alternating spacings of 1.25 inches (31.75 mm) and 0.5 inches (12.70 mm) The EIA standard was revised again in 1992 to comply with the 1988 public law 100-418 , setting the standard U as 15.875 mm (0.625 in) + 15.875 mm (0.625 in) + 12.7 mm (0.500 in), making each U 44.45 millimetres (1.75 in). The 19-inch rack format has remained constant while

4096-460: Was first replaced by clearance-hole (Round Hole, Round Unthreaded Holes, and Versa Rail ) racks. The holes are large enough to permit a bolt to be freely inserted through without binding, and bolts are fastened in place using cage nuts . In the event of a nut being stripped out or a bolt breaking, the nut can be easily removed and replaced with a new one. Production of clearance-hole racks is less expensive. The next innovation in rack design has been

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