Open Stack

Trying to orchestrate a bunch of VMs on our ~500 core cloud, and we're 
getting the "not enough hosts" problem.  Only issue is that the 
dashboard seems to imply we've got the elbow room needed to instantiate. 
  Furthermore, it would be *really handy* if I knew what the bottleneck 
it thought was: disk, RAM, CPU, whatever.  Here's a sample of the error:

----------------------- begin -----------------------
2016-07-28 18:40:47.961 1080 WARNING nova.scheduler.utils 
[req-977badf4-a4a2-4766-87fd-c4e3ceb2e293 
a4c895a6fe294ae3a81e3c6bb9209f52 33c2cf3cb61c425abcb0e0d35fdf21b7 - - -] 
[instance: ee175a40-11d9-4a43-b6e1-c4d7935acff1] Setting instance to 
ERROR state.
2016-07-28 18:40:51.892 1023 WARNING nova.scheduler.utils 
[req-e2a65200-1662-4cd7-aa9e-db5e225adfa1 
a4c895a6fe294ae3a81e3c6bb9209f52 33c2cf3cb61c425abcb0e0d35fdf21b7 - - -] 
Failed to compute_task_build_instances: No valid host was found. There 
are not enough hosts available.
Traceback (most recent call last):

   File "/usr/lib/python2.7/dist-packages/oslo_messaging/rpc/server.py", 
line 142, in inner
     return func(*args, **kwargs)

   File "/usr/lib/python2.7/dist-packages/nova/scheduler/manager.py", 
line 84, in select_destinations
     filter_properties)

   File 
"/usr/lib/python2.7/dist-packages/nova/scheduler/filter_scheduler.py", 
line 90, in select_destinations
     raise exception.NoValidHost(reason=reason)

NoValidHost: No valid host was found. There are not enough hosts 
available.
----------------------- begin -----------------------

Any suggestions on how to track down exactly what's going wrong?

Thanks!

-Ken