首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
If you have lots of unused storage space on your hard disk, then why not share it with others on the Internet? The benefit could
If you have lots of unused storage space on your hard disk, then why not share it with others on the Internet? The benefit could
admin
2019-08-01
48
问题
If you have lots of unused storage space on your hard disk, then why not share it with others on the Internet? The benefit could be distributed storage for your own files, making them available any time via the web, even if you are nowhere near your computer—indeed, even if your computer is switched off. That idea is what a Zurich-based firm called Caleido is aiming to provide, with a free online storage service known as Wuala that was recently introduced to the public.
【R1】______In particular, its developers, Dominik Grolimund and Luzius Meisser, have used a clever mathematical trick to compensate for the fact that the participating computers will come and go from the internet in an unpredictable way.
【R2】______Copying costs participants both storage space and bandwidth.
Yet there have to be enough copies to ensure that there is at least one available most of the time. If, for example, each computer is online 25% of the time, then a quick calculation shows that you would have to copy each file to 100 different computers to ensure that 999,999 times out of a million there is at least one copy available when a user looks.
【R3】______Instead, Mr. Grolimund and Mr. Meisser plan to break each file into chunks, which can be scattered liberally around the hard disks of participating computers, and then to use a mathematical trick to reconstruct the original file from those chunks.
【R4】______The first step is to convert the file(which is, regardless of what it represents, simply a long string of ones and zeros)into a mathematical function called a polynomial. This is done by splitting it into 100 fragments, which are smaller binary numbers. It is these numbers that are used to define the polynomial. All you have to do is select a suitable number of points from along the polynomial and convert their values into the appropriate mathematical constructs. Scatter these around the host computers and, when someone wants to look at the file, he need recover only 100 of them to have enough data to reconstruct the file from scratch. To have 100 points available 999,999 times out of a million it turns out that you need to scatter a total of 600 of them around. That is an amount of data equivalent to six versions of the original file. Moreover, the system needs the computers linked to it to be available for only 17% of the time, rather than 25% , for this to apply.
【R5】______Most commercial online-storage services use centralized servers. Although these are generally reliable, they do sometimes fail. And when they do, the results are embarrassing.
Though some people may feel sick about scattering their data over hundreds of other computers(even though it will be encrypted), or storing unknown file fragments on their own, Mr Grolimund is sure that Caleido has learnt from other "peer-to-peer" file-sharing systems, and that Wuala is built to handle concerns about the illegal distribution of copyrighted or " inappropriate" content.
[A]This trick, known as Reed-Solomon error correction, is employed routinely to interpret the data on DVDs, but it has not been used before in the volatile world of private computers on the Internet.
[B]One of the characteristics of a polynomial is that a few numbers can nail it down precisely. If a simple polynomial is plotted out on a graph it forms a line.
[C]Online storage is a growing market, especially for backing up data, where reliability is a big concern.
[D]The challenge is how to minimize the number of copies of the same file that have to be distributed.
[E]It has been proved that for online data storage, Wuala is as good to give as it is to receive.
[F]Though the idea underlying it is simple, Wuala requires some nifty technology to make its distributed system work reliably.
[G]But copying every file a hundred times is hugely inefficient.
【R3】
选项
答案
G
解析
上文中提到拷贝的重要性,并举例说明如果每一台电脑有25%的时间在线,那么每份文件需要有100份拷贝以确保在用户查找的时候,在100万次中至少有999999次有一份拷贝可供利用。本段后文说到Wuala的两位开发者希望能够通过数学技巧来解决问题,说明本段第一句提及了一个问题,通过比较备选项,可知[G]为正确答案。
转载请注明原文地址:https://jikaoti.com/ti/Yg87FFFM
0
考研英语一
相关试题推荐
UnderstandingwhatdistinguishespeoplewhobattlewithAlzheimer’sastheyagefromthosewhosementalacutenessremainsstrong
What’stheenginethatdrivesAmericanbusiness?Innovation?Sweat?Capital?Trycoffee.Fromtheshopfloortotheboardroom,J
Themajortaskfacingadolescentsistocreateastableidentity.Therearesomedevelopmentaltasksthatenablethemtocreate
RonaldP.RohneroftheUniversityofConnecticuthasspentsomeyearslookingattheconsequencesforchildrenandteenagersof
RonaldP.RohneroftheUniversityofConnecticuthasspentsomeyearslookingattheconsequencesforchildrenandteenagersof
Organisedvolunteeringandworkexperiencehaslongbeenavitalcompaniontouniversitydegreecourses.Usuallyitisleftto【C
Organisedvolunteeringandworkexperiencehaslongbeenavitalcompaniontouniversitydegreecourses.Usuallyitisleftto【C
WhydoesPeterDruckercontinuetoenjoysuchahighreputation?Partoftheanswerliesinpeople’smixedemotionsaboutmanage
Ifyouwereawomanreadingthismagazine40yearsago,theoddsweregoodthatyourhusbandprovidedthemoneytobuyit.That
随机试题
测定糕点的过氧化值含量时,游离的碘用氢氧化钠标准溶液滴定。
亚急性感染性心内膜炎全身感染的表现有
以下不属于化生的是
A.肺动脉栓塞B.急性心肌梗死C.肺炎球菌肺炎D.结核性胸膜炎E.自发性气胸男性,60岁。行左膝关节手术后第2天出现晕厥,持续3分钟。当时BP85/35mmHg,轻微气短,无胸痛,无咯血。心电图示:电轴右偏,顺钟向转位。最可能的诊断是
活髓牙全冠修复应采用的粘固剂是义齿基托通常采用
“备案号”栏:()。“单价”栏:()。
保险经纪人能解决保险市场上的( )问题,降低交易成本,所以保险经纪人有利于保险市场机制的完善。
发生以下()情形的,期货交易所应当解散。
甲公司发生下列有关交易性金融资产的业务:(1)2013年1月8日,甲公司购入丙公司发行的公司债券,该笔债券于2012年7月1日发行,面值为2500万元,票面利率为4%,债券利息按年支付。甲公司将其划分为交易性金融资产,支付价款为2600万元(
目前。全球面临的危机大体上分为两类:一类是由市场自己产生因而也能被市场_______的危机,比如当下的金融危机。另一类是受外生条件的_______,市场不能解决的危机,比如土地、空气、矿产资源、石油、天然气等等,不是随着价格提高就能增加产品供给量、增强资源
最新回复
(
0
)