Cloud computing has given the new face to the distributed field. Two main issues are discussed in this paper, (I) the process of finding the efficient virtual machine by using the concept of load balancing algorithm. (II) Reallocation of the Virtual Machines i.e. migration of the Virtual Machines when cloud provider is not available with the required Virtual Machines. We have discussed about the different load balancing algorithms which are used for deciding the efficient Virtual Machine for the allocation to the client on demand. While in the second issue is concern we have discuss about different modules available for the migration of Virtual Machines from one source machine to the other target machine. At last discussion about the different simulators available for the cloud are carried out in this paper.
