What is the reliability of distributed systems

Reliability of three elements:

availability, security and fault tolerance are described below.

 1. Availability

•  portion of the time remains available for the system to be used.

•  Try to reduce the dependency between the servers as it increase the chance can.

•  Key elements should be replicated to improve availability.

2. Security

• Securing every information in a distributed OS. 

• Cannot trust the ID field in messages.

• Also coding of content to keep the information secure in the network. 

• Secure Sockets Layer (SSL) provides this type of security.

3. Tolerance of Mistakes

• This refers to the system's ability to tolerate mistakes. 

• This is often achieved by multiple instances of a resource.

• In case of a crash, the server should recover the data without affecting the work.

• Things that can cause a crash should not be done.

• One should have the ability to change numbers at will.

• Efficiency decreases when a system crashes or stops being used.

• If one server crashes, the other servers will distribute its workload in a row.hardware for distributed systems Handles.

What hardware is there for distributed systems

(a) Distributed systems, i.e. multiple instruction streams and multiple 

(b) have MMID hardware are title-tied (Tightly coupled hardware)

•  There is very little delay between sending the notifications.

• Data is sent at high speed. 

• Mostly used in parallel systems.

• Parallel Algorithm: Processors work on the same problem. 

(c) Hardware is loosely coupled (Loosely coupled hardware) - there is

• more delay between sending messages.

• Data is sent at a slow speed.

(d) Multiprocessor 

• A distributed system in which processors share the same memory, that is, they share the same virtual address .

• Symmetric Multi Processor (SMP) All processors are of the same type. 

(e) Multi-Computer

• A distributed system where processors do not share the same memory.

• Usage : a collection of personal computers that are connected to a network.

(f) Bus system

• A distributed system consisting of back planes, buses, cables and of connecting all processors in a single network other means.

(g) SWID system

• A distributed system in which wires are used to connect each machine to another machine. There are different ways of wiring.

• Information is sent through wires.

• Switching decisions are made sequentially along the route. 

(h) Multi-processor based on bus

• Many processors have the same memory.

• Efficiency decreases when the workload on the bus is high (when multiple CPUs are connected to the bus). 

• Adding cache memory allows additional CPUs to be added before there is too much workload on the bus. 

What are the software for distributed systems

include the following software for distributed

(a) network operating system

• Be connected loose associated software for hardware (multi-computer).

• Network of computers The

• OS may be different on each machine. 

• Usage : Linux machines lab.

(b) Integrated Distributed System

• Software mounted tightly on dolly hardware,

• a compilation of several machines that do not have memory but function as a single machine.

(c) Multiprocessor time sharing system 

• tightly coupled hardware to tightly coupled software.

• Example: Unix machine with multi processors.

• Shared Memory.

• A small scheduler queue (kept in shared memory).

• Example - Grundl (SGI supercomputer with 24 processors)

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