  Cloud Computing (CC) is a model for enabling on-demand access to a shared
pool of configurable computing resources. Testing and evaluating the
performance of the cloud environment for allocating, provisioning, scheduling,
and data allocation policy have great attention to be achieved. Therefore,
using cloud simulator would save time and money, and provide a flexible
environment to evaluate new research work. Unfortunately, the current
simulators (e.g., CloudSim, NetworkCloudSim, GreenCloud, etc..) deal with the
data as for size only without any consideration about the data allocation
policy and locality. On the other hand, the NetworkCloudSim simulator is
considered one of the most common used simulators because it includes different
modules which support needed functions to a simulated cloud environment, and it
could be extended to include new extra modules. According to work in this
paper, the NetworkCloudSim simulator has been extended and modified to support
data locality. The modified simulator is called LocalitySim. The accuracy of
the proposed LocalitySim simulator has been proved by building a mathematical
model. Also, the proposed simulator has been used to test the performance of
the three-tire data center as a case study with considering the data locality
feature.
