characterizationofdistributedsystems-全文預(yù)覽
【正文】 ery ? . Roll back ? Redundancy ? . IP route, replicated name table of DNS Concurrency ? Correctness ? ensure the operations on shared resource correct in a concurrent environment ? . records bids for an auction ? Performance ? Ensure the high performance of concurrent operations Transparency ? Access transparency ? using identical operations to access local and remote resources ? . a graphical user interface with folders ? Location transparency ? resources to be accessed without knowledge of their location ? . URL ? Concurrency transparency ? several processed operate concurrently using shared resources without interference with between them ? Replication transparency ? multiple instances of resources to be used to increase reliability and performance without knowledge of the replicas by users or application programmers Transparency (contd.) ? Failure transparency ? users and applications to plete their tasks despite the failure of hardware and software ponents, ., ? Mobility transparency ? movement of resources and clients within a system without affecting the operation of users and programs, ., mobile phone ? Performance transparency ? allows the system to be reconfigured to improve performance as loads vary ? Scaling transparency ? allows the system and applications to expand in scale without change to the system structure or the application algorithms Summary ? Distributed systems are pervasive ? Distributed puting and resource sharing are primary motivations for constructing distributed systems ? Characterization of Distributed System ? Concurrency ? No global clock ? Independent failures Summary (contd.) ? Challenges to construct distributed system ? Heterogeneity ? Openness ? Security ? Scalability ? Failure handling ? Concurrency ? Transparency 。 Web增長 ? Load on the first Web server () 1000 times what it has been 3 years earlier Web增長 ? 網(wǎng)站數(shù)目 ↑ ↑ ↑ ? 19931996, from 130 to 600,000 sites ? Netcraft said that In the September 2020 survey we received responses from 135,166,473 sites. This is an increase of million sites since last month How does Netcraft do this? 用戶數(shù)量增長 ? 中國互聯(lián)網(wǎng)絡(luò)信息中心（ CNNIC） 《 第十八次中國互聯(lián)網(wǎng)絡(luò)發(fā)展狀況統(tǒng)計報告 》 ? 截止到 2020年 6月 30日，我國網(wǎng)民人數(shù)達到了 人，與去年同期相比增長了 % 瀏覽器大戰(zhàn) ? 1993， Mark Andreessen編寫 Mosaic ? “The great thing abo
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