<转>CloudSim 讨论组提的问题

【介绍】为了促进对CloudSim的研究学习，参考全球对云计算仿真工具CloudSim感兴趣科研人员在google讨论组(http://groups.google.com/group/cloudsim)的交流内容提供给群友学习，内容均为讨论组成员对CloudSim疑惑的交流，由CLOUDS实验室的人员予以解答，看看里面有你关心的问题吗，你若有问题也可以发邮件至[e-mail]

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【2011-8-18】
1.【主题】：Cloudlet Scheduling
Hi team,
Can anyone explain what is the use of "bindCloudletToVm" function ( in DatacenterBroker) when we have CloudletSchedular ???
【状态】已回复
This method is used in our sample of broker to force it to schedule a Cloudlet in a specific VM. If this method is not use, the cloudlet will be send to any free VM.

if I bind a cloudlet to a VM, is it possible to schedule it on another VM later (using some scheduling algorithms)?

The broker supplied in the code is an example only. We really expect that people develop their own policies for this purpose. Therefore, if you don't want to force a cloudlet to go to a specific VM, don't implement the method in your broker (or don't use this method even if it is implemented).
【2011-8-16】
1.【主题】：Workflow scheduling  
hi everyone
i am doing research in workflow scheduling in cloud environment. Can i implement the scheduling policies for workflows on clouds using
cloudsim? or any example in cloudsim that will do the same? thanks in advance
【状态】待回复....

2.【主题】VM allocation
Hello,
I am trying to run the DVFS example and I have a question regarding the  optimization of allocation in the
PowerVmAllocationPolicySingleThreshold class.

In the optimizeAllocation() method, in the test :

" if (allocatedHost != null && allocatedHost.getId() != oldHost.getId()) "

if a VM from "vmsToMigrate" list remains on the same host after reallocation (allocatedHost = oldHost), the VM will not be recreated on the host. However, the VM has previously been destroyed on the oldHost. Therefore, new VMs that may be allocated afterwards on the same host will not take into account (when tested for available resources) the resource allocation to VMs that remain there. Is it necessary to have "allocatedHost.getId() != oldHost.getId()" in the test above?
Thank you,
【状态】已回复
Hi !
    About "the VM has previously been destroyed on the oldHost.", the Vm information have been save to vmsToRestore. The destroyed Vms will be restored by restoreAllocation(vmsToRestore, getHostList()) In the behind of optimizeAllocation() method.

【2011-8-15】
【主题】About the high load experiment of datacenter
Hi everyone,
   I attempt the DVFS example. To get the performance of the high load, I change implementation of the DVFS.java as the following. Only
function CreateClouletList was modified .I change the load with the method of changing "clouletsNumber"variable. The result of running is unexpected. I sometimes encounter the error prompt"[VmScheduler.vmCreate] Allocation of VM #13 to Host #0 failed by MIPS  Something is wrong, the VM can's be restored", but other times it works well. I can't apprehend the result. How to avoid
the error? Is it a bug? Thanks.

private static List<Cloudlet> createCloudletList(int brokerId) {
               List<Cloudlet> list = new ArrayList<Cloudlet>();
               long length = 150000; // 10 min on 250 MIPS
               int pesNumber = 1;
               long fileSize = 300;
               long outputSize = 300;
               //for (int i = 0; i < cloudletsNumber; i++) {
               for (int i = 0; i < 55; i++) {
                       Cloudlet cloudlet = new Cloudlet(i, length,
pesNumber, fileSize,
outputSize, new UtilizationModelStochastic(), new
UtilizationModelStochastic(), new UtilizationModelStochastic());
                       cloudlet.setUserId(brokerId);
                       //cloudlet.setVmId(i);
                       list.add(cloudlet);
               }
               return list;
}
【状态】已回复
Hi!

The UtilizationModelStochastic() uses random numbers to determine utilization of CPU by a Cloudlet. Eventually, if there are too many
Cloudlets in one VM, the random allocation may cause cloudlets to need more power than the VM has.

To avoid it, you can submit less cloudlets to each vm, increase VM capacity, or utilize another UtilizationModel.

【2011-8-14】
【主题】Problem With SingleThreshold
Hi

I see some problems in simulating Singlethresold.java. I have set the followings for running the algorithm:
hostsNumber =100
VmsNumber =290
CloudletsNumber = 290
ram = 128
bw = 2500
size = 2500

But it gives me this error! :

"Allocation of VM #71 to Host #1 failed by BW
Something is wrong, the VM can not be restored"

What is the problem? Have I set wrong parameters?
【状态】已回复
You have too many hosts with few hosts bandwidth, so it is impossible to make the virtual machine migrations. Try increasing the hosts
bandwidth from 100 Mbps to 1 Gbps, or decreasing VMs bandwidth, and your problem should go away.