Midterm Flashcards
Learn material from first 5 weeks (141 cards)
What is meant by a distributed system?
a group of computers working together as to appear as a single computer to the end-user.
What are the 4 main goals of a distributed system?
- Making resources accessible
- Distribution transparency
- Openness
- Scalability
What are the different types of transparency?
- Access transparency
- Location transparency
- Migration transparency
- Relocation transparency
- Replication transparency
- Concurrency transparency
- Failure transparency
Hide differences in data representation and how a resource is accessed.
Access transparency
Hide where a resource is located.
Location transparency
Hide that a resource may move to another location.
Migration transparency
Hide that a resource may be moved to another location while in use.
Relocation transparency
Hide that a resource is replicated
Replication transparency
Hide that a resource may be shared by several competitive users.
Concurrency transparency
Hide the failure and recovery of a resource.
Failure transparency
A distributed system that is able to present itself to users and applications as if it were only a single computer system is said to be __________.
transparent
A(n) ___________ is a system that offers services according to standard rules that describe the syntax and semantics of those services.
open distributed system
Characterizes the extent by which two implementations of systems or components from different manufacturers can co-exist and work together, by merely relying on each other’s services as specified by a common standard.
Interoperability
Characterizes to what extent an application developed for a distributed system A can be executed, without modification, on a different distributed system B that implements the same interface as A.
Portability
The notion that it should be relatively easy to add parts that run on a different operating system, or even to replace an entire file system.
Extensibility
List the three dimensions by which scalability can be measured,
- size
- geographically
- administratively
What is meant by scalability of size?
We can easily add more users and resources to the system.
What is meant by geographic scalability?
A system in which the users and resources may be far apart.
What is meant by administrative scalability?
It can still be easy to manage even if it spans many independent administrative organizations.
What are three scaling techniques?
- hiding communication latency
- distribution
- replication
Trying to avoid waiting for a response to remote (and potentially distant) service requests as much as possible.
Hiding communication latency
This involves taking a component, splitting it into smaller parts, and subsequently spreading those parts across the system.
Distribution
Name one real-world example of distribution.
DNS tree of domains that are divided into non-overlapping zones.
This technique increases availability, but also helps to balance the load between components, leading to better performance.
Replication