Overview of Performance Testing and types of performance testing

Performance Testing finds out the speed and efficiency of the system, computer, product or device. Performance testing is testing that is performed, to determine how fast some aspect of a system performs under a particular workload. A software related performance problem can easily get identified through performance testing.
Performance testing demonstrate that the system meets performance criteria. It can compare two systems to find which performs better. It can also measure what parts of the system or workload causes the system to perform badly.

Types of Performance Testing

1.Load Testing : A load test is usually conducted to understand the behavior of the application under a specific expected load. Examples of load testing include:
- Downloading a series of large files from the Internet.
- Running multiple applications on a computer or server simultaneously.
- Assigning many jobs to a printer in a queue.

2.Stress Testing: It determines the load under which a system fails, and how it fails. There are various varieties of Stress Tests, including spike, stepped and gradual ramp-up tests.
3.Volume Testing: It test what happens if huge amounts of data are handled.
4.Soak Testing: The system is runm at high levels of load for prolonged periods of time.
5.Configuration Testing: The process of testing a system with each of the configurations of software and hardware that are supported.
7.Timing testing: It evaluates response times and time to perform an action.

Overview of Distributed File Systems (DFS)

A distributed file system or network file system is any file system that allows access to files from multiple hosts sharing via a computer network. This makes it possible for multiple users on multiple machines to share files and storage resources.
In order to understand the structure of a distributed file system, the terms service, server and client should be defined. A service is a software entity running on one or more machines and providing a particular type of function. A server is the service software running on a single machine. A client is a process that can invoke a service using a set of operations that forms its client interface.
A distributed file system (DFS) is a file system whose clients, servers, and storage devices are dispersed among the machines of a distributed system. A service activity has to be carried out across the network, and instead of a single centralized data repository, there are multiple and independent storage devices. the distinctive features of a DFS are the multiplicity and autonomy of clients and servers in the system.
A DFS should look to its clients like a conventional, centralized file system. The client interface of a DFS should not distinguish between local and remote files. The most important performance measurement of a DFS is the amount of time needed to satisfy various service requests. In a DFS, a remote access has the additional overhead attributed to the distributed structure. This overhead includes the time needed to deliver the request to the server, as well as the time for getting the response across the network back to the client. DFS manages a set of dispersed storage devices which is the DFS's key distinguishing feature.