The growing popularity of cloud computing in both research and academia has introduced cloud as one of the focus area of future research. However, researchers who want to analyze their applications performance on cloud or to test their scheduling algorithms on cloud do not have the opportunity to work with real cloud test beds because of the huge expenditure involved in the setup of the same. So, to promote research in the area of cloud computing the best that can be done is to provide researchers with cloud simulation tools on which they can test their applications and algorithms. Here we have collected few simulator name and it description/facility/overview as given on them website or author.
Simulation appears to be the only feasible way to analyses algorithms on large-scale distributed systems of heterogeneous resources. Unlike using the real system in real time, simulation works well, without making the analysis mechanism unnecessary complex, by avoiding the overhead of co-ordination of real resources. Simulation is also effective in working with very large hypothetical problems that would otherwise require involvement of a large number of active users and resources, which is very hard to coordinate and build at large-scale research environment for investigation purpose.
To promote research in the area of grid computing, various popular simulators are available viz.
1. Gridsim 
The GridSim toolkit allows modeling and simulation of entities in parallel and distributed computing (PDC) systems-users, applications, resources, and resource brokers (schedulers) for design and evaluation of scheduling algorithms.
Overview of GridSim functionalists: 
- Incorporates failures of Grid resources during run-time.
- New allocation policy can be made and integrated into the GridSim Toolkit, by extending from AllocPolicy class.
- Has the infrastructure or framework to support advance reservation of a grid system.
- Incorporates a functionality that reads workload traces taken from supercomputers for simulating a realistic grid environment.
- Incorporates an auction model into GridSim.
- Incorporates a data grid extension into GridSim.
- Incorporates a network extension into GridSim. Now, resources and other entities can be linked in a network topology.
- Incorporates a background network traffic functionality based on a probabilistic distribution. This is useful for simulating over a public network where the network is congested.
- Incorporates multiple regional GridInformationService (GIS) entities connected in a network topology. Hence, you can simulate an experiment with multiple Virtual Organizations (VOs).
- adds ant build file to compile GridSim source files.
2. Simgrid 
SimGrid is a scientific instrument to study the behavior of large-scale distributed systems such as Grids, Clouds, HPC or P2P systems. It can be used to evaluate heuristics, prototype applications or even assess legacy MPI applications. All this as free software.
SimGrid provides ready to use models and API to simulate many different distributed systems: clusters, wide-area and local-area networks, peers over DSL conations, data centers, etc.
- SimGrid as a Grid Simulator: Accurate yet fast simulation models
- SimGrid as a P2P Simulator: Highly scalable simulations
- SimGrid as an MPI Simulator: Realistically simulates unmodified MPI programs
- SimGrid as a Cloud Simulator: SimGrid provides an libvirt-like interface for your Cloud simulation
3. OptorSim 
OptorSim is a Grid simulator designed to test dynamic replication strategies used in optimizing the efficiency of a Grid.
4. GangSim 
GangSim is a tool developed for Grid scheduling studies, capable of supporting studies for controlled resource sharing based on uSLAs.
5. CloudSim 
Toolkit supports modeling and creation of one or more virtual machines (VMs) on a simulated node of a Data Center, jobs, and their mapping to suitable VMs. It also allows simulation of multiple Data Centers to enable a study on federation and associated policies for migration of VMs for reliability and automatic scaling of applications.
Overview of CloudSim functionalists:
- support for modeling and simulation of large scale Cloud computing data centers
- support for modeling and simulation of virtualized server hosts, with customizable policies for provisioning host resources to virtual machines
- support for modeling and simulation of energy-aware computational resources
- support for modeling and simulation of data center network topologies and message-passing applications
- support for modeling and simulation of federated clouds
- support for dynamic insertion of simulation elements, stop and resume of simulation
- support for user-defined policies for allocation of hosts to virtual machines and policies for allocation of host resources to virtual machines
6. CloudAnalyst 
CloudAnalyst is built directly on top of CloudSim  toolkit, leveraging the features of the original framework and extending some of the capabilities of CloudSim. It is a tool developed at the University of Melbourne whose goal is to support evaluation of social networks tools according to geographic distribution of users and data centers. In this tool, communities of users and data centers supporting the social networks are characterized and, based on their location; parameters such as user experience while using the social network application and load on the data center are obtained/logged.
7. GreenCloud 
Provides a simulation environment for energy-aware cloud computing data centers. GreenCloud is designed to capture details of the energy consumed by distributed environments. Greencloud is a sophisticated packet-level simulator for energy-aware cloud computing data centers with a focus on cloud communications. It offers a detailed fine-grained modeling of the energy consumed by the data center IT equipment, such as computing servers, network switches, and communication links.
8. NetworkCloudSim 
Supports modeling of real Cloud data centers and generalized applications such as HPC, e-commerce and workflows. Out of all the above simulators,
9. WorkflowSim 
WorkflowSim extends the CloudSim simulation toolkit by introducing the support of workflow preparation and execution with an implementation of a stack of workflow parser, workflow engine and job scheduler. It supports a multi-layered model of failures and delays occurring in the various levels of the workflow management systems. A series of popular workflow scheduling algorithms (e.g., HEFT, Min-Min, and Max-Min) and task clustering algorithms have been implemented in WorkflowSim. Parameters are directly learned from traces of real executions that were run by workflow management systems such as Pegasus. WorkflowSim has been developed by Weiwei Chen and team at University of Southern California, USA.
10. SimpleWorkflow 
This is a simple package containing classes helping in simulating workflows on CloudSim. This is not as comprehensive as WorkflowSim, but it utilizes the same workload description files than Workflows.
11. DynamicCloudSim 
DynamicCloudSim extends the CloudSim simulation toolkit by introducing models for (1) heterogeneity in the performance of computational resources, (2) uncertainty in and dynamic changes to the performance of virtual machines, and (3) straggler machines and failures during task execution.
12. RealCloudSim 
RealCloudSim provides a graphical interface to read network topologies based on the BRITE format. RealCloudSim also uses its own engine to simulate allocations based on Genetic Algorithms, Mixed Integer Programming with Lingo software, and network simulations based on the NS2 (Network Simulator 2). A complete report is generated at the end of each simulation.
13. CloudReports 
CloudReports is a graphic tool that simulates distributed computing environments based on the Cloud Computing paradigm. It uses CloudSim as its simulation engine and provides an easy-to-use user interface, report generation features and creation of extensions in a plugin fashion.
14. CloudAuction 
This works extends Cloudsim by developing a package library that enables CloudSim to handle auction-based services. The main objective of this research is implementing auction-based mechanisms in Cloudsim. To test the package library, a new market mechanism to efficently allocate services to participants based on the combinatorial double auction principle was implmented. The mechanism considers the relevant attributes applicable in Cloud computing environments to the benefit and satisfaction of both users and providers. In this package library, the auction is held based on cost for CPU MIPS and the remainig characteristics (bandwidth, RAM size, etc.) are regarded on VM side if they match the request.
15. CloudMIG Xpress 
CloudMIG Xpress facilitates the comparison and planning phases concerning the migration of software systems to PaaS or IaaS-based Cloud environments.
Citation http://www.buyya.com/gridsim/ as on May 27, 2014  http://simgrid.gforge.inria.fr/ as on May 27, 2014  http://www.gridpp.ac.uk/demos/optorsimapplet/ as on May 27, 2014  http://people.cs.uchicago.edu/~cldumitr/GangSim/ as on May 27, 2014  http://www.cloudbus.org/cloudsim/ as on May 27, 2014  http://greencloud.gforge.uni.lu/ as on May 27, 2014
Note: This site Contain “As Is” definition on given citation. Credit of description goes to each website or author.