OOP AND DISTRIBUTED SYSTEMS Flashcards
What is a distributed system
• A distributed system is a network that consists of autonomous
computers that are connected using a distribution middleware.
• They help in sharing different resources and capabilities to
provide users with a single and integrated coherent network.
“A distributed system is one in which hardware or software
components located at networked computers communicate and
coordinate their actions only by message passing.”
Draw a diagram showing a distributed system
*See notes for pics(2)
Give differences between centralized and decentralized Systems
• Centralized Systems
– Centralized systems have non-autonomous components
– Centralized systems are often build using homogeneous technology
– Multiple users share the resources of a centralized system at all times
– Centralized systems have a single point of control and of failure
• Distributed Systems
– Distributed systems have autonomous components
– Distributed systems may be built using heterogeneous technology
– Distributed system components may be used exclusively
– Distributed systems are executed in concurrent processes
– Distributed systems have multiple points of failure
What is the relationship between Distributed systems and computer networks
Every distributed system relies on services provided by a
computer network.
Networks focuses on packets, routing, etc., whereas distributed
systems focus on applications.
Give examples of distributed systems
- Internet
- Intranet
- Mobile/Ubiquitous Computing
- Automatic Teller Machine Network
Describe the basic model for giant-scale services. Use a diagram
Clients connect via the Internet and then go through a load manager that hides down nodes and balances traffic.
*See notes for pic
What is the focus for the basic model for giant-scale services.
- High availability
- Replication
- Degradation
- Disaster tolerance
- Online evolution
Give examples of giant-scale services
- Aol
- Microsoft network
- Yahoo
- eBay
- Amazon
- CNN
What are the advantages of the basic model that giant-scale services follow
- Access anywhere, anytime
- Availability via multiple devices
- Groupware support
- Lower overall cost
- Simplified service updates
Give a brief listing of the reasons why there is need for distributed systems
- Technological changes
- User needs
- Functional separation
- Inherent distribution
- Power imbalance and load variation
- Reliability and economies
Describe technological changes as a motivation for distributed systems
l Growth in microelectronics (e.g., VLSI – Very Large Scale
Integration, etc) has enabled price-performance ratio to
favor multiple low-performance processors rather than
single high-performance processors.
l Interconnection and communication costs have fallen
dramatically – LANs, etc are now readily available and cost-
effective.
Describe user needs as a motivation for distributed systems
l Increased desire to provide computing power (processing)
where it is needed. Users need more sophisticated facilities
– faster, reliable, etc.
l There is also managerial desire to decentralize.
Describe functional separation as a motivation for distributed systems
– Existence of computers with different capability & purpose:
- Clients and Servers
- Data collection and data processing
Describe inherent distribution as a motivation for distributed systems
• Information – Different information is created and maintained by different persons (e.g., Web pages);
• People
– Computer supported collaborative work (virtual
teams, engineering, virtual surgery)
• Retail store and inventory systems for supermarket
chain
Describe power imbalance and load variation as a motivation for distributed systems
• Distribute computational load among different computers
