com.cloud.exception.InsufficientServerCapacityException what wrong?

["Jake.liu" <he...@sina.com>]

com.cloud.exception.InsufficientServerCapacityException: Unable to create a deployment for VM[User|14e221fe-1285-49b7-b18f-4911bdfa2880]Scope=interface com.cloud.dc.DataCenter; id=1
	at org.apache.cloudstack.engine.cloud.entity.api.VMEntityManagerImpl.reserveVirtualMachine(VMEntityManagerImpl.java:186)
	at org.apache.cloudstack.engine.cloud.entity.api.VirtualMachineEntityImpl.reserve(VirtualMachineEntityImpl.java:198)
	at com.cloud.vm.UserVmManagerImpl.startVirtualMachine(UserVmManagerImpl.java:3864)
	at com.cloud.vm.UserVmManagerImpl.startVirtualMachine(UserVmManagerImpl.java:3458)
	at com.cloud.vm.UserVmManagerImpl.startVirtualMachine(UserVmManagerImpl.java:3444)
	at com.cloud.utils.component.ComponentInstantiationPostProcessor$InterceptorDispatcher.intercept(ComponentInstantiationPostProcessor.java:125)
	at org.apache.cloudstack.api.command.user.vm.DeployVMCmd.execute(DeployVMCmd.java:379)
	at com.cloud.api.ApiDispatcher.dispatch(ApiDispatcher.java:162)
	at com.cloud.async.AsyncJobManagerImpl$1.run(AsyncJobManagerImpl.java:437)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
	at java.util.concurrent.FutureTask.run(FutureTask.java:166)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
	at java.lang.Thread.run(Thread.java:679)
INFO  [cloud.vm.UserVmManagerImpl] (UserVm-Scavenger-1:) Found 1 vms to expunge.