Aria Automation Day 2 Update Fails with "SCSIController and UnitNumber already assigned"

Products

• VCF Operations/Automation (formerly VMware Aria Suite)

Issue/Introduction

When transitioning from Aria Automation Orchestrator 8.x based disk provisioning to native Aria Automation template properties, users may encounter deployment failures during Day 2 operations (such as resizing CPU or RAM).

This occurs after updating a cloud template to include explicit SCSIController and unitNumber properties or modifying constraints tags.

Common Error Message:

SCSIController [SCSI_Controller_#] and UnitNumber [#] is already assigned, cannot be assigned to disk [vm_#_disk_1[#]]

Environment

VMware Aria Automation 8.x

VMware Aria Automation Orchestrator 8.x

Cause

The root cause is a product limitation regarding non-updatable (immutable) storage properties during the reconciliation process.

Aria Automation's engine interprets the addition of a unitNumber or the modification of constraints (storage profile tags) on an existing resource as a request to recreate or reassign that resource. Because the disk is already physically attached to that SCSI slot in vCenter, the validation logic triggers a conflict error. Furthermore, changing storage constraints triggers a code path that attempts to delete and recreate the disk to satisfy the new policy, which is not supported as an "in-place" update.

Resolution

To resolve this issue, the configuration must be aligned with the initial deployment state of the disks to avoid triggering recreation logic.

1. Revert Disk Property Changes for Existing Deployments

For VMs that are already deployed, ensure the template version used for Day 2 updates does not contain the new unitNumber, SCSIController, or modified constraints tags.

• Compare the current template with the version used during the initial build.

• Remove the explicit SCSI mapping if it was not present during the first "Provision" operation.

2. Implement Conditional Template Logic

To support both new and existing builds, use conditional logic within the cloud template. This ensures that only new deployments receive the explicit disk mapping.

• New Builds: Use the updated template with explicit unitNumber.

• Existing Builds: Maintain a "Legacy" template version or use logic to skip these properties for existing resources.

3. Manual Storage Policy Alignment

If you must update the storage policy (via constraints) for an existing disk:

• Perform the change directly within vCenter Server.

• Aria Automation cannot relocate or re-apply storage policies to existing disks via constraint changes once the disk has been provisioned.