# 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.

```ruby
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.
```

## 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 [\[max\_units\]](https://docs.openstack.org/osc-placement/queens/cli/index.html) allocation.

## Diagnostics

#### On underlying host:

1. Get the VM disk storage path using command given below:

```bash
$ sudo virsh domblklist <VM_UUID>
```

```ruby
$ sudo virsh domblklist <VM_UUID>
 Target   Source
-------------------------------------------------------------------------
 vda      _opt_data_instances_[VM_UUID]_disk
```

2. 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.

```bash
$ df -lh _opt_data_instances_<VM_UUID>_disk
```

```ruby
$ sudo df -lh _opt_data_instances_[VM_UUID]_disk
Filesystem                         Size  Used Avail Use% Mounted on
[Disk dev mapper path]             98G   69G   25G  74% _
```

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:

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

```bash
$ openstack resource provider list
```

4. 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.

```bash
$ openstack resource provider inventory list <RESOURCE_PROVIDER_UUID>
```

```ruby
$ 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 | 
+----------------+------------------+----------+----------+----------+-----------+--------+-------+
```

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

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

## Validation

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

```bash
$ openstack image list --all | grep -i <IMAAGE_USED_BY_VM>
$ openstack image show <IMAGE_UUID> --fit
```

```ruby
+------------------+-----------------------------------------------------------------------+
| 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]                                                          |
...                .                                                                       .
+------------------+-----------------------------------------------------------------------+
```

2. If these steps prove insufficient to resolve the issue, reach out to the [Platform9 Support Team](https://support.platform9.com/hc/en-us) for additional assistance.


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