This projects provides a single simulation scenario that can be run in CloudSim Plus 4.3.0 and 5.2.2.
It uses a VmAllocationPolicySimple which implements a Worst-Fit policy
to allocate Hosts to VMs. VM scheduling is performed by a VmSchedulerSpaceShared policy.
CloudSim Plus 4 uses the same implementations of VmAllocationPolicy provided by CloudSim.
That implementation relies on HashMaps to keep track of the number of used PEs by each Host.
That makes finding a Host to place a VM computationally complex in large scale experiments.
CloudSim Plus 5 provides new, simpler and faster implementations of those policies.
The simulation scenario is compounded of as below
Objects |
Amount |
Configuration for each individual object |
Hosts |
2 |
8 PEs of 1000 MIPS |
VMs |
5 |
4 PEs of 1000 MIPS |
Cloudlets |
1 for each VM |
4 PEs of 1000 MIPS, length of 10000 MI |
As you can see by the table above, we can place 2 VMs in each Host. Since we have 2 Hosts, we can run 4 VMs. However, it’s requested the creation of 5 VMs. Therefore, one VM will fail to be created. Since each Cloudlet created will be bound to a specific VM, if a given VM cannot be created due to lack of available physical resources, then its Cloudlets could not be executed.
However, running the simulation using CloudSim Plus 4 (as explained in the next section), one of the VMs will fail. However, the Cloudlet previously bound to it will be placed inside another available VM. Such a behaviour is performed by the DatacenterBroker, as implemented in CloudSim. That is a surprising and unexpected behaviour. If you want a Cloudlet to run in any VM available, you just don’t bind it to a VM. If you do that, you are telling that it must run specifically on that VM.
Therefore, using CloudSim Plus 4, you may not see some Cloudlets failing because they are allocated in some VM anyway.
In CloudSim Plus 5, if a Cloudlet is bound to a VM and that VM is not created, the Cloudlet is not executed. If you want the broker to choose where to run a Cloudlet, simply don’t bind it to a VM. The broker will do that.