Must know of advantages and disadvantages


  1. What is the role of middleware in a distributed system?
    1. A distributed system is blablabla first, and then answer the question.

Chapter 1: goals

  1. Explain what is meant by distribution transparency, and give examples of different types of transparency.
    1. Distribution transparency is the phenomenon by which distribution aspects in a system are hidden from users and applications. Examples include access transparency, location transparency, migration transparency, relocation transparency, replication transparency, concurrency transparency, failure transparency and persistence transparency.
  1. What is an open distributed system and what benefits does openness provide?
    1. An open distributed system is blablabla
  2. Describe precisely what is meant by a scalable system
    1. A system is scalable with respect to its number of components, geographical size or number and size of administrative domains, if it can grow in one or more of these dimensions without an unacceptable loss of performance.
  3. Scalability can be achieved by applying different techniques. What are these techniques?
    1. Distribution, replication and caching.

Chapter 1: hardware concepts

  1. What is the difference between a multiprocessor and a multi-computer
    1. In a multiprocessor, the CPUs have access to a shared main memory. There is no shared memory in multi-computer systems, the CPUs can communicate only through message passing.
  2. What is the drawback of multiprocessor systems?

a.       Bus, all trying to contact the memory using the bus

                                                               i.      Scalability is an issue

                                                             ii.      Solution: cache

1.      What is cache?

a.       Memory

2.      What is a problem with cache?

a.       Consistency: local copy can be wrong

    1. How can we improve this scalability issue?

Chapter 1: Software concepts

  1. What is the difference between a distributed operating system and a network operating system?
    1. A distributed operating system manages multiprocessors and homogenous multi-computers. A network operating system connects different independent computers that each have their own operating system so that users can easily use the services available on each computer.

Chapter 4: Naming

Naming play an important role in all computer systems

They are used to

        Share resources

        Uniquely identify entities

        Refer to locations and so on

Name resolution thus allows a process to access the named entity

To resolve names it is necessary to implement a naming system

In a distributed system the implementation of a naming system is itself often distributed across multiple machines.

How the distribution is done plays a key ole in the efficiency and scalability of the naming system.

We will concentrate on three different important ways that names are used in distributed systems:

Mangle noe her


A name space implementation slide 23 og 24

A name space forms the heart og a naming service

A service that allows users and processes to add, remove and lookup names


Basic issue: Distribute the name resolution process as well as name space management across multiple machines bu distributing nodes of thenaming graph

Consider a hierarchical naming graph and distinguish three levels

        Global level

        Admin level

        Managerial level


Slide 28 Iterative name resolution II

Slide 30 Recursive name resolution II


Chapter 6:


Reasons for replication: slide 4

Problems with replication: slide 5

Shared objects: slide 6



Strict consistency: slide 15, 16

Sequential consistency: slide 17, 18

Causal consistency: slide 21, 23

FIFO consistency: slide 25

Release consistency: 33

Entry consistency:


Monotonic reads: slide 46,

Monotonic write

Read you writes: slide 53


Chapter 7


Dependability: slide 5, 7

Terminology II: slide 9, 10


Failure masking: slide 14,15

Flat groups vs. hierarchical groups: slide 17

Reliable RPC II: Slide 27, 28, 30


Agreement in faulty systems: