The MSS (as it was known) consisted of a library of cylindrical plastic cartridges, two inches wide and 4 inches (100 mm) long, each holding a spool of tape 770 inches (20 m) long storing 50MB. These cartridges were held in a hexagonal array of bins in the IBM 3851 Mass Storage Facility. New cartridges were rolled into the facility and were automatically stored in a vacant bin. The data was accessed via one or two IBM 3330 disk drives, the data being transferred automatically between cartridge and disk drive in processes called staging and destaging. These were all connected together with the IBM 3830 Storage Control (also used for disk storage alone), the entire system making up a 3850 unit.
Cartridges were moved into and out of read stations by two motorized accessor arms, electrically connected via flat cable on a drum. Stage time for data from cartridge to disk was typically 15 seconds, including about two seconds to move the cartridge into a read station, and eight to ten seconds to read the 200-foot tape.
The recording method was unusual for its time. The tape was wound around a cylindrical mandrel in a helix and stopped. The drive head rotated once (on a rotating drum) to record a diagonal track. Then tape was wound a small step, so the head could iterate over next diagonal track. Depending on technical definitions this might be even considered a first example of a digital helical scan recording, long before Exabyte's helical drive (which was based on analog video helical recording systems developed earlier).
When free disk space was required a group of cylinders were selected to be destaged to tape, these were transferred with minimal or no change of format. Each tape could store 202 cylinder images of 19 tracks each, half of the 404 cylinders in a 3330 disk pack. Cylinder locations on the tape were fixed and identified by markers along the edge.
Read more about this topic: IBM 3850
Other articles related to "description":
... Universal Description, Discovery and Integration (UDDI, pronounced Yu-diː) is a platform-independent, Extensible Markup Language (XML)-based registry by which ... It is designed to be interrogated by SOAP messages and to provide access to Web Services Description Language (WSDL) documents describing the ...
... a dominant impression, using descriptive language, and organizing the description are the rhetorical choices to be considered when using a description ... A description is usually arranged spatially but can also be chronological or emphatic ... The focus of a description is the scene ...
... He gives a vivid and accurate description of the last colony of the European Beaver in Wales on the River Teifi, but spoils it by repeating the legend that beavers castrate themselves to avoid danger ... Likewise he gives a good description of an Osprey fishing, but adds the mythical detail that the bird has one webbed foot ... His description of Irish wildlife was harshly called "worthless" the better view perhaps is that despite its faults it gives a valuable glimpse of Irish fauna in the 1180s ...
... Unlike the keywords attribute, the description attribute is supported by most major search engines, like Yahoo! and Bing, while Google will fall back on this tag when information about the page itself is ... The description attribute provides a concise explanation of a Web page's content ... This allows the Web page authors to give a more meaningful description for listings than might be displayed if the search engine was unable to ...
Famous quotes containing the word description:
“It is possibleindeed possible even according to the old conception of logicto give in advance a description of all true logical propositions. Hence there can never be surprises in logic.”
—Ludwig Wittgenstein (18891951)
“Everything to which we concede existence is a posit from the standpoint of a description of the theory-building process, and simultaneously real from the standpoint of the theory that is being built. Nor let us look down on the standpoint of the theory as make-believe; for we can never do better than occupy the standpoint of some theory or other, the best we can muster at the time.”
—Willard Van Orman Quine (b. 1908)
“It [Egypt] has more wonders in it than any other country in the world and provides more works that defy description than any other place.”
—Herodotus (c. 484424 B.C.)