Open Stack

On 01/06/2015 03:56 AM, ppnaik wrote:
> Hi All,
> I have a multi node setup of openstack juno on centos 7. After I
> instantiate multiple VMs and check the nova-compute.log on compute nodes
> it shows a negative value for free disks even though the the physical
> system has a lot of free memory

I think you meant free *disk* :)

> on the physical system. df -h
>
> Filesystem               Size  Used Avail Use% Mounted on
> /dev/mapper/centos-root   50G  2.0G   49G   4% /
> devtmpfs                  16G     0   16G   0% /dev
> tmpfs                     16G     0   16G   0% /dev/shm
> tmpfs                     16G  281M   16G   2% /run
> tmpfs                     16G     0   16G   0% /sys/fs/cgroup
> /dev/mapper/centos-home  865G   33M  865G   1% /home
> /dev/sda1                494M  137M  358M  28% /boot
>
> nova-compute.log on compute node:
>
> 2015-01-06 11:00:28.756 8123 AUDIT nova.compute.resource_tracker [-]
> Total physical ram (MB): 31911, total allocated virtual ram (MB): 17920
> 2015-01-06 11:00:28.756 8123 AUDIT nova.compute.resource_tracker [-]
> Free disk (GB): -113
> 2015-01-06 11:00:28.757 8123 AUDIT nova.compute.resource_tracker [-]
> Total usable vcpus: 16, total allocated vcpus: 10
>
> What is the issue and how can I resolve it? Please help.

If you log into your SQL database for Nova and run the following query, 
what does it say?

SELECT SUM(root_gb + ephemeral_gb) AS total_gb
FROM instances
WHERE node = $compute_node;

Replace $compute_node with the value of the compute node's 
"hypervisor_hostname" field in the compute_nodes table.

Also, what is the value of your nova.conf instances_path option? From 
looking at the above, it looks like you have /home partitioned to 
contain most of the disk space, and / only has 49G available. If the 
default instances_path value is used (/var/lib/nova/instances for 
Debian-based systems, not sure about CentOS), then you will be using 
that 49G / mount and not the 895G /home mount.

Best,
-jay