Sistemas Operativos y Comunicacion de Datos - Mario Farias

Sistemas Operativos
Distribuidos (Parte 2)
M. en C. Mario Farias-Elinos
1
Contenido
Migración
Soporte al Sistema operativo
Comunicación entre procesos
Servicio de nombres
Sistema de archivos
2.2.2
1
Modelo de migración
Alternatives for code migration.
2.2.3
Migración en un sistema heterogeneo
3-15
2.2.4
2
Implementación del agente de migración.
Arquitectura de Agentes de Tanenbaum
2.2.5
Agentes de un sistema distribuido
Propiedad
Común para
Descripción
todos
Autonomía
Si
Capacidad de actuar por ellos mismos
Reactivo
Si
Responds timely to changes in its environment
Proactivo
Si
Iniciar acciones que afecten el ambiente
Communicativo
Si
Pueden intercambiar información con usuarios y/o
otros agentes
Continuo
No
Tener un tiempo de vida largo
Mobil
No
Capacidad de migrar de un sitio a otro
Adaptivo
No
Capacidad de aprendizaje
Propiedades importantes de un agente.
2.2.6
3
Tecnología de agentes
Modelo general de un agente
2.2.7
Capas del sistema
Applications, services
Middleware
OS: kernel,
libraries &
servers
OS1
Processes, threads,
communication, ...
OS2
Processes, threads,
communication, ...
Computer &
network hardware
Computer &
network hardware
Node 1
Node 2
Platform
2.2.8
4
Funcionalidad del Kernel
Process manager
Communication
manager
Thread manager
Memory manager
Supervisor
2.2.9
Copy-on-write
Process A’s address space
RA
Process B’s address space
RB copied
from RA
RB
Kernel
A's page
table
Shared
frame
B's page
table
a) Before write
b) After write
2.2.10
5
Kernel monolítico VS µkernel
S4
.......
S1
S1
Key:
Server:
S2
S3
S2
S3
S4
.......
.......
Monolithic Kernel
Microkernel
Kernel code and data:
Dynamically loaded server program:
2.2.11
Integración del microkernel
Middleware
Language
support
subsystem
Language
support
subsystem
OS emulation
subsystem
....
Microkernel
Hardware
The microkernel supports middleware via subsystems
2.2.12
6
Activación del Scheduler
Process
A
P added
SA preempted
Process
B
Process
SA unblocked
SA blocked
Kernel
Virtual processors
A. Assignment of virtual processors
to processes
P idle
Kernel
P needed
B. Events between user-level scheduler & kernel
Key: P = processor; SA = scheduler activation
2.2.13
Cliente/Servidor bajo threads
Thread 2 makes
requests to server
Thread 1
generates
results
Input-output
Receipt &
queuing
T1
Requests
N threads
Client
Server
2.2.14
7
Otras formas de servidores con
threads
per-connection threads
workers
I/O
I/O
remote
objects
remote
objects
a. Thread-per-request
per-object threads
b. Thread-per-connection
remote
objects
c. Thread-per-object
2.2.15
Llamadas serializadas y concurrentes
Serialised invocations
process args
marshal
Send
Receive
unmarshal
process results
process args
marshal
Send
Concurrent invocations
process args
marshal
Send
transmission
process args
marshal
Send
Receive
unmarshal
execute request
marshal
Send
Receive
unmarshal
process results
Receive
unmarshal
execute request
marshal
Send
Receive
unmarshal
execute request
marshal
Send
Receive
unmarshal
process results
Receive
unmarshal
execute request
marshal
Send
time
Receive
unmarshal
process results
Client
Server
Client
Server
2.2.16
8
Comunicación entre procesos
(a) System call
Control transfer via
trap instruction
Thread
Control transfer via
privileged instructions
User
Kernel
Protection domain
boundary
(b) RPC/RMI (within one computer)
Thread 1
User 1
Thread 2
Kernel
User 2
(c) RPC/RMI (between computers)
Network
Thread 1
Thread 2
User 1
User 2
Kernel 1
Kernel 2
2.2.17
El sistema X-Window
Esquema básico del X-Window
2.2.18
9
Esquema general
3.7
a)
b)
Client-to-server binding using a daemon as in DCE
Client-to-server binding using a superserver as in UNIX
2.2.19
Distribución del espacio de nombes
Ejemplo del DNS
2.2.20
10
Ejemplo del servicio DNS
URL
http://www.cdk3.net:8888/WebExamples/earth.html
DNS lookup
Resource ID (IP number, port number, pathname)
55.55.55.55 8888 WebExamples/earth.html
Web server
Network address
file
2:60:8c:2:b0:5a
Socket
2.2.21
Interactuación con el DNS
NS2
2
Client
1
NS1
Name
servers
3
NS3
A client iteratively contacts name servers NS1–NS3 in order to resolve a name
2.2.22
11
Búsqueda Recursiva y no recursiva en el
DNS
NS2
NS2
2
2
1
1
NS1
client
client
3
4
4
3
NS1
5
NS3
NS3
Non-recursive
server-controlled
Recursive
server-controlled
A name server NS1 communicates with other name servers on behalf of a client
2.2.23
Interactuación entre servidores DNS
a.root-servers.net
(root)
ns1.nic.uk
(uk)
uk
purdue.edu
yahoo.com
ns.purdue.edu
(purdue.edu)
co.uk
ac.uk
ns0.ja.net
(ac.uk)
* .purdue.edu
ic.ac.uk
qmw.ac.uk
dcs.qmw.ac.uk
*.qmw.ac.uk
*.dcs.qmw.ac.uk
alpha.qmw.ac.uk
(qmw.ac.uk)
dns0.dcs.qmw.ac.uk
(dcs.qmw.ac.uk)
*.ic.ac.uk
dns0-doc.ic.ac.uk
(ic.ac.uk)
2.2.24
12
Servicio de nombres por recurso
admin
Client
Printing
service
1. ‘finance’
lookup service?
admin
Client
Lookup
service
Network
2. Here I am: .....
4. Use printing
service
Corporate
infoservice
admin, finance
Printing
3. Request
printing
Lookup
service
service
finance
2.2.25
Estructura del X.500
2.2.26
13
Ejemplo del uso del X.500
X.500 Service (root)
... France (country)Great Britain (country)
Greece (country)
...
... BT Plc (organization)University of Gormenghast (organization)
...
... Computing Service (organizationalUnit)
Department of Computer Science (organizationalUnit)
Engineering Department (organizationalUnit)
...
... Departmental Staff (organizationalUnit)
ely (applicationProcess)
Research Students (organizationalUnit)
...
... Alice Flintstone (person)... Pat King (person)James Healey (person)Janet Papworth (person) ...
2.2.27
Esquema del GNS
DI: 599(EC)
DI: 543
DI: 574
AC
DI: 437
DI: 322
UK FR
QMW
Peter.Smith
mailboxes
Alpha
Beta
password
Gamma
2.2.28
14
Home-mobil
The principle of Mobile IP.
2.2.29
Escalabilidad
Creación de subnodos que comparten la información para
cubrir toda la red.
2.2.30
15
Sistema de almacenamiento
Compartido Persis- Replica/cache Mantenimiento Ejemplo
tente
distribuidos consistencia
Memoria principal
1
RAM
Sistema de archivos
1
UFS, FAT, NTFS
Sistema de archivos distribuido
Sun NFS
Web
Web server
Memoria distribuida compartida
Ivy
Objetos remotos (RMI/ORB)
1
CORBA
Almacenamiento de objetos
1
CORBA Persistent
Object Service
Almacenamiento de
objetos distribuidos
PerDiS, Khazana
2.2.31
Arquitectura del servicio de archivos
Client computer
Application Application
program
program
Server computer
Directory service
Flat file service
Client module
2.2.32
16
Arquitectura del NFS
Client computer
Server computer
Application Application
program
program
UNIX
system calls
UNIX kernel
Virtual file system
Local
UNIX
file
system
Other
file system
UNIX kernel
Virtual file system
Remote
NFS
client
NFS
server
NFS
protocol
UNIX
file
system
2.2.33
Arquitectura del NFS
2.2.34
17
Acceso al sistema de archivos local y
remoto
Server 1
Client
(root)
(root)
export
. . . vmunix
Server 2
(root)
usr
nfs
Remote
people
big jon bob . . .
mount
Remote
students
x
staff
mount
users
jim ann jane joe
2.2.35
Acceso al sistema de archivos local y
remoto
2.2.36
18
Automounting
2.2.37
Andrew File System (AFS)
Workstations
Servers
User Venus
program
Vice
UNIX kernel
UNIX kernel
User Venus
program
Network
UNIX kernel
Vice
Venus
User
program
UNIX kernel
UNIX kernel
2.2.38
19
Ejemplo del AFS
Local
Shared
/ (root)
tmp
bin
. . .
cmu
vmunix
bin
Symbolic
links
2.2.39
Llamadas del sistema en AFS
Workstation
User
program
Venus
UNIX file
system calls
Non-local file
operations
UNIX kernel
UNIX file system
Local
disk
2.2.40
20
Arquitectura del CFS
2.2.41
Arquitectura del CFS
2.2.42
21
Comunicación del CFS
2.2.43
Uso del servicio de nombres
2.2.44
22
Replicación en CFS
2.2.45
Operación de desconexión
2.2.46
23
Comparativa de xFS
Issue
NFS
Coda
Plan 9
xFS
Design goals
Access transparency
High availability
Uniformity
Serverless system
SFS
Scalable security
Access model
Remote
Up/Download
Remote
Log-based
Remote
Communication
RPC
RPC
Special
Active msgs
RPC
Client process
Thin/Fat
Fat
Thin
Fat
Medium
Server groups
No
Yes
No
Yes
No
Mount granularity
Directory
File system
File system
File system
Directory
Name space
Per client
Global
Per process
Global
Global
File ID scope
File server
Global
Server
Global
File system
Sharing sem.
Session
Transactional
UNIX
UNIX
N/S
Cache consist.
write-back
write-back
write-through
write-back
write-back
Replication
Minimal
ROWA
None
Striping
None
Fault tolerance
Reliable comm.
Replication and
caching
Reliable comm.
Striping
Reliable comm.
Recovery
Client-based
Reintegration
N/S
Checkpoint & write
logs
N/S
Secure channels
Existing mechanisms
Needham-Schroeder
Needham-Schroeder
No pathnames
Self-cert.
Access control
Many operations
Directory operations
UNIX based
UNIX based
NFS BASED
2.2.47
24