Nt1310 Unit 1 Distributed System

1 Introduction

As the technology developing, everything becomes computable. And when people realizing the importance of the Internet of Things, more and more data is collected. Analyzing such amount of data becomes a big challenge for modern people. As a very important component of our life, internet becomes indispensable. Data sharing between multiple users becomes more popular. It seems our life will stop if without the internet. The user devices becomes much lighter, most computing and data storage are separated with remote operations. Distributed system becomes more and more useful for our life.

1.1 Distributed system

A distributed system is a collection of independent computers (nodes) that appears to its users as a single coherent

Files location and operation are hidden to clients. Clients don’t need to know how the system is designed, how data is located and accessed, and how faults are detected. The logic name of the file should not be changed even when relocate the file. Client sends requests to handle files without thinking about the complex mechanisms of the underlying system which performs operations. The DFS server just provide an access to the system with some simple tools. DFSs also use local caching for frequently used files to eliminate network traffic and CPU consumption caused by repeated queries on the same file and represent a better performance. And the local caching also give a fast access to those frequently used files. So caching has a performance transparency by hiding data distribution to users. DFSs have their own mechanisms to detect and correct the faults, so that users do not be aware that such fault

DFS guarantees clients all functionality all the time when clients are connected to the system. By replicating files and spreading them into different nodes, DFS gives us a reliability of the whole file system. When one node has crash, it can service the client with another replica on different node. DFS has a reliable communication by using TCP/IP, a connection-oriented protocols. Once a failure occurred, it can immediately detect it and set up a new connection. For the single node storage, DFS uses RAID (Redundant Array of Inexpensive/Independent Disks) to prevent hard disk drive failure by using more hard disk, uses journal technique or strategy to prevent inconsistency state of the file system, and uses an UPS (Uninterruptible Power Supply) to allow the node to save all critical data.

2.3 Scalability

DFS promises that its system can be extended by adding more nodes to accommodate data’s growing. Also it can remove those not frequently used data from overloaded nodes to those light nodes to reduce network traffic. Scalability is the capability of a system, network, or process to handle a growing amount of work, or its potential to be enlarged in order to accommodate that growth.

2.4 Fault