The Filter Scheduler (nova.scheduler.filter_scheduler.FilterScheduler) is the 
default scheduler for scheduling virtual machine instances. It supports 
filtering and weighting to make informed decisions on where a new instance 
should be created. This Scheduler can only be used for scheduling compute 
requests, not volume requests, i.e. it can only be used with the 
compute_scheduler_driver configuration option

--



Here is how it picks up the node (in the exact order):

1.            Check the disk space - in your it is tiny flavor so no size check 
is done

2.            Check the memory - it does allow you provision beyond 1.5x 
(default) of physical memory. For example, if you have 72 GB physical memory, 
and each tiny flavor takes 512 MB (0.5 GB), the no. of instances that can be 
provisioned must not be more than (72*1.5)/0.5 =216 instances

3.            Check the CPU - it does not allow you provision vCPUs beyond 16x 
(default) of the physical core no. For example, if you have 24 cores, the 
scheduler will not consider the host that has more than 16x24= 384 vCPUs. In 
case of tiny flavor, it maps to 384 instances (1 vcpu each).



For further reading: 
http://docs.openstack.org/developer/nova/devref/filter_scheduler.html


From: Diego Parrilla SantamarĂ­a [mailto:[email protected]]
Sent: Wednesday, August 21, 2013 3:43 PM
To: Steve Heistand
Cc: [email protected]
Subject: Re: [Openstack] oversubscribe node

Try to put those options in the nova.conf file that the nova-scheduler process 
reads, not in the nova-compute servers.

Cheers
Diego

 --
Diego Parrilla
CEO
www.stackops.com<http://www.stackops.com/> |  
[email protected]<mailto:[email protected]> | +34 649 94 43 
29 | skype:diegoparrilla
<http://www.stackops.com/>

[http://stackops.s3-external-3.amazonaws.com/STACKOPSLOGO-ICON.png]


On Wed, Aug 21, 2013 at 11:56 PM, Steve Heistand 
<[email protected]<mailto:[email protected]>> wrote:
Hi folks,

so  Im a little confused, on my compute nodes I have the allocation ratio set:

root@node004:~# cat /etc/nova/nova-compute.conf
[DEFAULT]
..
cpu_allocation_ratio=1.0
ram_allocation_ratio=1.0
...

but I got into a state where the node is oversubscribed.  From nova 
hypervisor-show node004:

node004
..
vcpus_used              36
memory_mb_used  72837
memory_mb            64379
vcpus                       32
..

I have zones/aggregates set up and of the instances, one was started in just 
launch it anywhere mode and another was told to start on
a zone that is this node.

In looking back I would have expected the zone specified instance be rejected.

is this to be expected or a bug?

thanks

s


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