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Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
disk actuator a mechanical device that moves the disk arms over the disk surface(s) in order to position the read/write head(s) over the correct disk track. disk arm a mechanical assembly that positions the head over the correct track for reading or writing a disk device. The arm is not movable on a fixed-head disk, but is on a moving-head disk. disk array a number of disks grouped together, acting together as a single logical disk. By this, multiple I/O requests can be serviced in parallel, or that the bandwith of several disks can be harnessed together to service a single logical I/O request. disk cache a buffer memory area in main memory used to hold blocks of data from disk storage. The cache can hide much of the rotational and seek latencies in disk accesses because a complete data block (disk sector) is read or written together. Disk caches are normally managed by the machine's operating system, unlike a processor cache, which is managed by hardware.
8 Sizing up Servers
Published in Wes Simpson, Howard Greenfield, IPTV and Internet Video:, 2012
Wes Simpson, Howard Greenfield
Video servers are often made up of a number of physically separate hard disk drives and processors. This is done both for greater reliability and for better performance. Reliability is increased through the use of Redundant Array of Inexpensive Disks (RAID) technologies, which store extra data for each file. Extra data can be used with a simple algorithm to replace any data lost due to a failure or replacement of one of the disk drives. Multiple disk drives are used to increase the storage capacity of the total system beyond what is available on a single disk and also to increase the speed at which files can be written or read from the disk array. Similarly, multiple processors are used to enable the system to continue operating even if one processor fails and to provide greater computing power than would be available from a single processor.
The Basic Elements of Artificial Intelligence
Published in Frank M. Groom, Stephan S. Jones, Artificial Intelligence and Machine Learning for Business for Non-Engineers, 2019
Disk arrays – Larger disk storage units contain arrays of inexpensive disks with a processor in the same unit controlling access to the enclosed disk array. In data centers, the application programs have their large databases of information stored on these disk arrays which are then accessed over a data center-wide storage network. Similar to the clustered rows of computers, disk arrays are placed in racks and then rows of these disk arrays are clustered together.
Experimental Setup for Harmonic Impedance Measurement in a Real HV Power Grid
Published in Electric Power Components and Systems, 2019
Dariusz Borkowski, Andrzej Wetula, Jakub Kowalski, Szymon Barczentewicz, Jerzy Nabielec, Marek Rogóż, Ireneusz Szczygieł
Sampled voltages and timestamps are sent from the slave unit to the master unit using dedicated Ethernet interface. In the master, samples of measured currents are joined with received samples of voltages and sent to the data server by another, separate Ethernet interface. Data server is a Dell T20 server unit equipped with 4-core CPU, 32 GB RAM and 2 TB RAID disk array running Debian Linux operating system. Operating system has been set up in a typical server configuration, with only selected communication related services enabled and without graphical environment.