The operation Resize failed. Error from vCenter: The hot-plug operation failed

Products

• VCF Operations/Automation (formerly VMware Aria Suite)

Issue/Introduction

When attempting to increase CPU, RAM, or a combination of both resources on a powered-on Virtual Machine through an orchestration tool like vRA, the operation fails with "The operation Resize failed. Error from vCenter: The hot-plug operation failed".

Even if Memory Hot Add is enabled. This failure occurs specifically on VMs where the CPU Hot Add feature is disabled.

A RAM-only upgrade typically completes successfully online, but the addition of a CPU change (even an increase) causes the failure if the request attempts an online, non-disruptive hot-add.

Environment

• Product: Aria Automation 8.18.x
• Component: VM Resize action, vCenter Integration

Cause

The resize operation fails because vCenter Server enforces the VM's configuration settings, which take precedence over the orchestration request.

1. Online Attempt: When a resize request is submitted for a powered-on VM (especially if the "Reboot Machine" option is not selected), vRA defaults to requesting a non-disruptive hot-add operation from vCenter.
2. Configuration Conflict: Since CPU Hot Add is Disabled on the VM, vCenter recognizes that the requested CPU change cannot be performed online.
3. API Rejection: vCenter's resource scheduler immediately rejects the request because the primary instruction (hot-add) failed to execute, returning the specific error "The hot-plug operation failed". vCenter does not automatically switch from a failed online operation to a disruptive power-down cycle.

Resolution

To successfully perform a CPU or combined CPU/RAM upgrade when CPU Hot Add is Disabled, vRA must be explicitly instructed to perform the disruptive power cycle sequence.

Workaround:

1. Select the "Reboot Machine" option in the resize request form within vRA. This forces vRA to execute the necessary disruptive sequence: Power Off>Apply Change>Power On.
2. If the change is intended to be non-disruptive, the CPU Hot Add feature must be explicitly enabled on the VM while the VM is powered off.

Note on Dependencies:
Hot Add features rely on support from the ESXi host version, the VM's Hardware Version, the Guest OS version, and VMware Tools. If Hot Add is disabled for these reasons, a power cycle is mandatory regardless of the orchestration request.

Additional Information

The Hot Plug configuration takes precedence over the "Reboot Machine" checkbox. If the configuration requires a power cycle, vCenter will enforce it. If the power cycle is not requested, vCenter will reject the online attempt. The observed behavior is expected.

Enable CPU Hot Add
https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/8-0/enable-cpu-hot-add.html#:~:text=Last%20Updated%20November%205%2C%202025,5.0%20or%20later.