Photo by Seirei Christopher, Toshimasa Uemura [Photo: Atsushi Ma]
[High school baseball] "Dual wield director" who became the principal conditionally
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It was built while there were many teachers who opposed the accommodation itself, and the occupancy rate was low.
Mr. Toshimasa Uemura was the commander of Hamamatsu Sho and Kakegawa Nishi, and was described by Koshien seven times as a "reversal sacred slave" and a "miracle sacred slave."Holy in Shizuoka Prefecture ... → Continue reading
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Usability(Kayosei, English: availability; availability) Is the degree and ability of the system to operate continuously.
Availability is in English availability It is a translation for.Indicates the degree of "usability" from the user's point of view.The definitions in the major standards are as follows.
- JIS X 0014: 1999 "Information Processing Terms-Reliability, Maintainability and Availability"
- The ability of a functional unit to perform a required function at a given time or for a certain period of time under certain conditions when the necessary external resources are given.
- JIS X 5004: 1991 "Basic reference model for interconnection between open systems-safety protection system"
- Properties that can be accessed and used when requested by an authorized entity
- JIS Q 20000-1: 2012 "Information Technology-Service Management-Part 1: Service Management Requirements"
- The ability of a service or service component to perform the requested function over a pre-agreed time or period.
Regarding reliability and maintainability, which are the other two of RAS, reliability means that hardware and software fail less frequently and the period of failure is short, availability means that users can use it, and maintainability means maintenance. Refers to being easy to do.
These three are often confused, but they need to be considered separately from the perspective of troubleshooting.In general, the lower the reliability and the more failures, the lower the availability.However, even if a failure occurs, the impact on availability can be minimized if it is made redundant or if the effects of the failure are mitigated and localized successfully.In addition, if maintainability is low, repair time when a failure occurs, inspection and backup time during normal operation, etc. become long, and overall availability is limited.
The idea of using the three elements of RAS as evaluation indicatorsIBMIs largeComputer(main frame)ofSystem / 370Series1970 It begins with the announcement in June. System / 61964 Was a general-purpose computer developed and sold by IBMSystem / 360It is the successor to the series. IBM has adopted a new RAS concept in this new System / 370 model and appealed for its new value as a product..
At that time, they competed for services with the same functions and performance as IBM computers.Fujitsuと日立2 companies are also IBMCompatible machineAsM seriesShared the market.From the standpoint of a compatible machine, this M series also incorporates the RAS function sung by IBM...Due to such circumstances, with RAS, after that, "I"When"SWas addedRASISIs currently widely used not only in the field of computersAcronymIt became a word as.
English adjectives available Has meanings such as useful and available, Its noun availability Japanese corresponding to is said to be effective and useful,When IBM Japan launched the System / 370 series to the Japanese market, "Availability in RAS sung by IBM in the United States, which is the head office, is a new word with novelty regardless of the translation of the English-Japanese dictionary.UsabilityWas called.
The numerical representation of availabilityOccupancy rateThe probability that repairable systems, equipment, parts, etc. maintain their functions at a specific moment (instantaneous operating rate), or the probability that they maintain their functions within a specified period of time. (Average utilization rate).The abbreviation is A.
|Occupancy rate||Inoperable time|
|99.999%||5 minutes 15 seconds|
|99.99%||52 minutes 34 seconds|
|99.9%||XNUM X hours X NUM X minutes|
|99%||3 days 15 hours 36 minutes|
- Mean failure interval (MTBF)
- Mean time to recovery (MTTR)
- RAMS (Terms that include reliability, maintainability, and safety in availability)
- HA(High availability, High-availability, Highly-available)
- Redundancy (redundancy)
- Single point of failure(SPOF: Single Point of Failure)
- Fault tolerant system
- ^ System / 370 RAS Facilities,National Institute of Informatics
- ^ II.The Era of Large Computer Development, [1962-1980], 8.3 Technology and Architecture, [Table 5. Overview of M-160 / M-180II / M-190], Features: Advanced RAS function,NiftyHome Page
- ^ Japanese translation of available goo dictionary
- ^ Japanese translation of availability goo dictionary