Access Transparency in Distributed Systems Quiz and Flashcards

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Questions and Answers

What is the importance of location transparency in a distributed system?

Location transparency is important because it allows resources to be moved without affecting how they can be accessed.

How does replication transparency ensure data availability in a distributed system?

Replication transparency ensures data availability by storing multiple copies of a resource, making it accessible even if one copy is unavailable.

What is the primary goal of concurrency transparency in a distributed system?

The primary goal of concurrency transparency is to hide the fact that resources are shared by multiple competitive users.

How does failure transparency contribute to the reliability of a distributed system?

Failure transparency hides the fact of failure and recovery of a particular resource, ensuring uninterrupted access to resources. Signup and view all the answers

What is the significance of persistence transparency in distributed systems?

Persistence transparency allows users to access resources without knowing whether they are stored in memory or storage. Signup and view all the answers

How does migration transparency facilitate resource relocation in a distributed system?

Migration transparency enables resources to be moved without affecting how they can be accessed, ensuring seamless relocation. Signup and view all the answers

How is the DNS name space organized?

The DNS name space is hierarchically organized into a tree of Domains, which are divided into non-overlapping Zones. Signup and view all the answers

What is the purpose of replication in a distributed system?

Replication increases availability and balances load between components, which leads to better performance. Signup and view all the answers

How does caching differ from replication?

Caching is a decision made by the client, whereas replication is a decision made by the owner of the resource. Signup and view all the answers

What is a drawback of caching and replication?

They can affect scalability, causing consistency problems due to modification in one copy making it different from the others. Signup and view all the answers

What is the purpose of resolving a name in the DNS?

Resolving a name means returning the network address of the associated host. Signup and view all the answers

Why is the DNS naming service distributed over several machines?

To avoid that a single server has to deal with all requests for name resolution. Signup and view all the answers

What is a major characteristic of Multicomputers?

Each machine has its own private memory. Signup and view all the answers

What are the two categories of interconnection networks based on architecture?

Bus and Switch. Signup and view all the answers

What is a key property shared by all CPUs in a Multiprocessor system?

All CPUs have direct access to shared memory. Signup and view all the answers

What is the main problem with Bus-based multiprocessors when there are a few CPUs?

The bus will usually be overloaded and performance drops drastically. Signup and view all the answers

What is the purpose of Cache memory in a Multiprocessor system?

It holds the most recently accessed words and acts as a high-speed buffer between the CPU and main memory. Signup and view all the answers

What is the coherent property of memory in a Multiprocessor system?

When CPU A writes a word to memory, and a microsecond later B reads that word, then B will get the value just written. Signup and view all the answers

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Study Notes

Location Transparency

Assigned logical names to resources, leaving no clue about the physical location of the resource (e.g., http://www.yahoo.com/index.html)
Enables resources to be moved without affecting access

Migration Transparency

Enables resources to be moved without affecting access

Relocation Transparency

Resources can be relocated while being accessed, without the user or application noticing
Example: mobile computer users

Replication Transparency

Hides the fact that a resource is replicated (storing multiple copies)
Requires all replicas to have the same name (achieved through location transparency)
Increases availability and balances load between components, leading to better performance

Concurrency Transparency

Hides the fact that resources are shared by several competitive users
Example: two independent users storing files in the same file server at the same time

Failure Transparency

Hides the fact of failure and recovery of a particular resource
One of the most complicated issues in Distributed Systems (DS) design

Persistence Transparency

Hides whether a resource is in memory (volatile) or storage (disk)
Example: object-oriented databases, where the database server copies the object's state to main memory, performs operations, and writes back to secondary storage

DNS Name Space

Hierarchically organized into a tree of domains, divided into non-overlapping zones
Each zone's names are handled by a single name server
Resolving a name returns the network address of the associated host

Distributed Systems

Physically distributed across large numbers of computers
Examples: WWW, DNS

Replication and Caching

Replication: storing multiple copies of a resource, increasing availability and balancing load
Caching: a special case of replication, where the copy is made by the client, usually in proximity to the client
Both replication and caching can affect scalability, causing consistency problems due to modifications in different copies
The extent of inconsistency tolerated depends on the resource's use (e.g., tolerable for internet tutorials)

Multicomputers

Each machine has its own private memory
Examples: bus-based and switch-based architectures

Multiprocessors

Share a single key property: all CPUs have direct access to shared memory
Bus-based multiprocessors consist of CPUs connected to a common bus and a memory module
Cache memory is used to improve performance by reducing bus overload