VM Deployment Failed Due to Insufficient Storage

Problem

VM deployment using Ephemeral storage fails with "No valid host was found" on ostackhost logs, and "insufficient resources or a temporary occurrence as compute nodes start up" error in Nova-scheduler logs.

Nova-scheduler logs
    
INFO nova.scheduler.manager [None [Req-UUID] [Project-ID] [User-ID] - - default default] Got no allocation candidates from the Placement API. This could be due to insufficient resources or a temporary occurrence as compute nodes start up.
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Environment

Self-Hosted Private Cloud Director Virtualization - v2025.4 and Higher
Self-Hosted Private Cloud Director Kubernetes - v2025.4 and Higher

Cause

VM deployment failed because the requested size surpassed the resource provider's max_unit allocation. Further details on [max_units] allocation.

Diagnostics

On underlying host:

Get the VM disk storage path using command given below:

Command
    
 
$ sudo virsh domblklist <VM_UUID>
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Example
    
 
$ sudo virsh domblklist <VM_UUID> Target   Source------------------------------------------------------------------------- vda      /opt/data/instances/[VM_UUID]/disk
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Check where the VM disk storage path is mounted.

The OpenStack placement API takes Disk dev mapper size into account when calculating the resource provider's max unit value.

Command
    
 
$ df -lh /opt/data/instances/<VM_UUID>/disk
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Example
    
 
$ sudo df -lh /opt/data/instances/[VM_UUID]/diskFilesystem                         Size  Used Avail Use% Mounted on[Disk dev mapper path]             98G   69G   25G  74% /
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Here,

VM disk storage path is mounted on "/".
The OpenStack consider this 98 GB size while calculating the resource provider's max unit value.

OpenStack CLI:

List down all available resource providers. These resource providers are responsible for allocating the CPU, Memory and Storage to the VMs.

Command
    
 
$ openstack resource provider list
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Check for max_unit for Disk_GB on all resource providers listed above.

Any VM requesting an ephemeral storage disk above the max_unit value will fail with "insufficient resources or a temporary occurrence as compute nodes start up" error in the nova-scheduler logs.

Command
    
 
$ openstack resource provider inventory list <RESOURCE_PROVIDER_UUID>
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Example
    
 
$ openstack resource provider inventory list <RESOURCE_PROVIDER_UUID>+----------------+------------------+----------+----------+----------+-----------+--------+-------+
| resource_class | allocation_ratio | min_unit | max_unit | reserved | step_size |  total |  used |
+----------------+------------------+----------+----------+----------+-----------+--------+-------+
| VCPU           |             16.0 |        1 |       80 |        0 |         1 |     80 |     6 |
| MEMORY_MB      |              1.5 |        1 |   773663 |      512 |         1 | 773663 | 12288 |
| DISK_GB        |           9999.0 |        1 |       97 |        0 |         1 |     97 |   120 | +----------------+------------------+----------+----------+----------+-----------+--------+-------+
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Here,

The DISK_GB for the resource provider is 97GB, a value determined by the VM's disk storage configured for the root (/) mount point.

Resolution

Use image which has storage requirements less than the max_unit value from all available resource providers.
It is recommended to use Cinder-backed volumes for VM deployments.

Validation

How much storage is requested by the image used to deploy VM.

Command
    
 
$ openstack image list --all | grep -i <IMAAGE_USED_BY_VM>$ openstack image show <IMAGE_UUID> --fit
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Example
    
 
+------------------+-----------------------------------------------------------------------+
| Field            | Value                                                                 |
+------------------+-----------------------------------------------------------------------+
...                .                                                                       .
| disk_format      | qcow2                                                                 |
| file             | /v2/images/[image_uuid]/file                                          |
| id               | [image_uuid]                                                          |
| min_disk         | 80            <----- Image requires 80 GB disk, within max_unit value || min_ram          | 0                                                                     |
| name             | [image_name]                                                          |
...                .                                                                       .
+------------------+-----------------------------------------------------------------------+
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If these steps prove insufficient to resolve the issue, reach out to the Platform9 Support Team for additional assistance.

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