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In August 1908, a white mob attacked Springfield, Illinois’s Black community, destroying homes and businesses and lynching two Black men. National outrage over the violence helped spur the movement that created the NAACP the following year.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It often implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache.
Disk array controller is often ambiguously shortened to disk controller which can also refer to the circuitry responsible for managing internal disk drive operations.
A disk array controller provides front-end interfaces and back-end interfaces.
A single controller may uses different protocols for back-end and for front-end communication. Many enterprise controllers use FC on front-end and SATA on back-end.
In a modern enterprise architecture disk array controllers (sometimes also called storage processors, or SPs[1]) are parts of physically independent enclosures, such as disk arrays placed in a storage area network (SAN) or network-attached storage (NAS) servers.
Those external disk arrays are usually purchased as an integrated subsystem of RAID controllers, disk drives, power supplies, and management software. It is up to controllers to provide advanced functionality (various vendors name these differently):
A simple disk array controller may fit inside a computer, either as a PCI/PCIe expansion card or just built onto a motherboard. Such a controller usually provides host bus adapter (HBA) functionality itself to save physical space. Hence it is sometimes called a RAID adapter.
As of February 2007[update] Intel started integrating their own Matrix RAID controller in their more upmarket motherboards, giving control over 4 devices and an additional 2 SATA connectors, and totalling 6 SATA connections (3 Gbit/s each). For backward compatibility one IDE connector able to connect 2 ATA devices (100 Mbit/s) is also present.
While hardware RAID controllers have been available for a long time, they initially required expensive Parallel SCSI hard drives and aimed at the server and high-end computing market. SCSI technology advantages include allowing up to 15 devices on one bus, independent data transfers, hot-swapping, much higher MTBF.
Around 1997, with the introduction of ATAPI-4 (and thus Ultra-DMA-Mode, which enabled fast data transfers with less CPU utilization) the first ATA RAID controllers were introduced as PCI expansion cards. Those RAID systems made their way to the consumer market, for users wanting the fault-tolerance of RAID without investing in expensive SCSI drives.
Fast consumer drives make it possible to build RAID systems at lower cost than with SCSI, but most ATA RAID controllers lack a dedicated buffer or high-performance XOR hardware for parity calculation. As a result, ATA RAID performs relatively poorly compared to most SCSI RAID controllers. Additionally, data safety suffers if there is no battery backup to finish writes interrupted by a power outage.
Because the hardware RAID controllers present assembled RAID volumes, operating systems aren't strictly required to implement the complete configuration and assembly for each controller. Very often only the basic features are implemented in the open-source software driver, with extended features being provided through binary blobs directly by the hardware manufacturer.
Normally, RAID controllers can be fully configured through card BIOS before an operating system is booted, and after the operating system is booted, proprietary configuration utilities are available from the manufacturer of each controller, because the exact feature set of each controller may be specific to each manufacturer and product. Unlike the network interface controllers for Ethernet, which can be usually be configured and serviced entirely through the common operating system paradigms like ifconfig in Unix, without a need for any third-party tools, each manufacturer of each RAID controller usually provides their own proprietary software tooling for each operating system that they deem to support, ensuring a vendor lock-in, and contributing to reliability issues.[2]
For example, in FreeBSD, in order to access the configuration of Adaptec RAID controllers, users are required to enable Linux compatibility layer, and use the Linux tooling from Adaptec,[3] potentially compromising the stability, reliability and security of their setup, especially when taking the long term view in mind.[2] However, this greatly depends on the controller, and whether appropriate hardware documentation is available in order to write a driver, and some controllers do have open-source versions of their configuration utilities, for example, mfiutil and mptutil is available for FreeBSD since FreeBSD 8.0 (2009),[4][5] as well as mpsutil/mprutil since 2015,[6] each supporting only their respective device drivers, this latter fact contributing to code bloat.
Some other operating systems have implemented their own generic frameworks for interfacing with any RAID controller, and provide tools for monitoring RAID volume status, as well as facilitation of drive identification through LED blinking, alarm management, hot spare disk designations and data scrubbing § RAID from within the operating system without having to reboot into card BIOS. For example, this was the approach taken by OpenBSD in 2005 with its bio(4) pseudo-device driver and the bioctl utility, which provide volume status, and allow LED/alarm/hotspare control, as well as the sensors (including the drive sensor) for health monitoring;[7] this approach has subsequently been adopted and extended by NetBSD in 2007 as well.[8]
With bioctl, the feature set is intentionally kept to a minimum, so that each controller can be supported by the tool in the same way; the initial configuration of the controller is meant to be performed through card BIOS,[7] but after the initial configuration, all day-to-day monitoring and repair should be possible with unified and generic tools, which is what bioctl is set to accomplish.
Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
A disk array controller is a device that manages the physical disk drives and presents them to the computer as logical units. It often implements hardware RAID, thus it is sometimes referred to as RAID controller. It also often provides additional disk cache. Disk array controller is often ambiguously shortened to disk controller which can also refer to the circuitry responsible for managing internal disk drive operations.
Xserve RAID is a attachment mass-storage server that was offered by Apple Inc. Xserve RAID held up to 14 hot-swappable Ultra-ATA hard drives, and had a capacity of 10.5 TB when filled with 750 GB modules. Xserve RAID supported RAID levels of 0, 0+1, 1, 3 and 5 in hardware, hybrid RAID levels such as 10 and 50 could be created in software. It was rack-mountable and was 3U high. Although the Xserve RAID contained 14 drives, they were split into two independent groups of 7 drives each managed by an identical RAID controller. Importantly, the controllers were independent, but not redundant; each managed seven of the storage array's fourteen drives, given a failure of one of the controllers those 7 drives were not accessible: the other could not take over its duties. Xserve RAID did, however, have redundant cooling units and power supplies. Xserve RAID's ports were two Fibre Channel ports for regular data transfer, a 10/100 Ethernet port for remote management, and a serial port for UPS communication via the Simple Signaling Protocol. Apple marketed Xserve RAID mainly as a companion to Xserve in file server and high-performance technical computing applications. The storage array is also useful in some environments such as non-linear video editing. Also, Apple certified Xserve RAID for use with some other vendors' servers, such as those running Windows Server 2003 or Red Hat Enterprise Linux. Due to the cross-platform support available, users do not need a Mac to administer the Xserve RAID. Apple shipped a CD-ROM with the device containing the Xserve RAID Admin Tools, a Java software application that runs on most operating systems — including OS X, Windows, Linux, and Solaris. Xserve RAID was available in models costing between US$5,999 and US$10,999 (later US$12,999), plus configuration and support options. The Xserve RAID was discontinued on February 19, 2008.
In computer hardware, a controller may refer to: Memory controller, a unit that manages access to memory Charge controller Game controller, a device by which the user controls the operation of the computer Host controller Sound controller Network controller Graphics controller or video display controller SCSI host bus adapter Parallel port controller Microcontroller unit (MCU) Keyboard controller Programmable interrupt controller Power management controller Northbridge (computing) Southbridge (computing) Universal asynchronous receiver/transmitter (UART) communications controller chip Peripheral DMA controller Disk controller Floppy disk controller Disk array controller, also known as a RAID controller, a type of storage controller Flash controller, or SSD controller, which manages flash memory Storage controller Terminal access controller IBM 2821 Control Unit, used to attach card readers, punches and line printers to IBM System/360 and IBM System/370 computers IBM 270x and IBM 37xx, used for telecommunications IBM 3271, 3272, 3271, and 3174, used to attach terminals (display devices) MIDI controller Programmable logic controller
Mylex Corporation was an American computer company active from 1983 to 1999. The company mainly produced peripherals and expansion cards for personal computers—chiefly the IBM Personal Computer—for the bulk of its existence, although it also produced complete motherboards. In the mid-1990s the company focused on designing and manufacturing RAID controllers, eventually cornering 75 percent of the RAID controller market. In 1999, the company was acquired by and made a subsidiary of IBM for approximately $240 million. In 2002, IBM sold their Mylex division to LSI Logic for an undisclosed amount.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.