8/16/2019 Practica Teo Rica 02

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2da Practica Teórica

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Sistemas Concurrentes y Distribuidos

Harp

1. We equip each serer !ith a sma"" UPS that a""o!s it to run #or a

short !hi"e $e.%.& a #e! minutes' a#ter a po!er #ai"ure( the serer

uses this time to copy in#ormation in the "o% to dis). The

combination o# the o"ati"e "o% and the *PS is one o# the noe"

features o# Harp.

2. The re"ated #i"e system !or) can be diided into three cate%ories+

pro,ects that proide a ne! #i"e system& pro,ects that support NFS

or VFS& and pro,ects that use "o%s but not replication.

-. Harp is intended to run in an enironment consistin% o# a

distributed co""ection o# nodes that communicate by means o# a

net!or). The net!or) mi%ht be a "oca" area net or a

%eo%raphica""y distributed net such as the nternet.

4. The primary maintains a "o% in o"ati"e memory in !hich it

records in#ormation about modi#ication operations. The "o%

contains a sequence o# eent records( each record describes an

operation& and records at hi%her indices describe more recent 

operations

a'/0T b'/S c'*PS d'S

e'bac)up

a'/0T b'*PS

c'S d'copy e'rep"ication #'TP

%'*DP

a'disp"ay b'per#ormance c' d'%o

e'run #' sites %'nodes

a're%isters b' processors

c'approach d'operation

#'process %'recent h'records

Pa3os

1. The Pa3os a"%orithm assumes a net!or) o# processes. n itsconsensus a"%orithm& each process p"ays the ro"e o# proposer &

acceptor & and "earner.

2. ssume that a%ents can communicate !ith one another by

sendin% messages.

-. %ents operate at arbitrary speed& may fail by stoppin%& and may

restart.

4. 5essa%es can ta)e arbitrari"y "on% to be delivered& can be

duplicated& and can be "ost& but they are not corrupted.

a'irtua" b'#ai"ure d'hard!aree'data

a'pac)a%es b'messa%es

c'commands d'!arnin%s

a'restart b'stop c'#ai" d'dup"icate

e'reboot

a'send b'dup"icates c'de"iered

d'moed e' remoed #'stoped