VM and Tenant Hot-Plug Capabilities

Understanding which resources can be modified on running VMs and tenants without requiring a restart, including drives, NICs, RAM, and CPU cores.

This article explains which resources can be modified on running virtual machines and tenants without requiring a power cycle, and which changes require a restart.

Virtual Machine Hot-Plug

The Allow Hotplug setting on a VM (enabled by default) controls whether drives and NICs can be added or removed while the VM is running.

What Can Be Hot-Plugged

Resource	Hot-Plug	Notes
Drives	Yes	Guest OS must support hot-add; Virtio-SCSI interface recommended
NICs	Yes	Widely supported by modern guest operating systems
Drive Resize	Yes	Virtio-SCSI drives can be expanded without power cycle; guest OS may need to rescan or extend filesystem

What Requires a Power Cycle

Resource	Power Cycle Required	Notes
RAM	Yes	Memory changes always require VM to be powered off and back on
CPU Cores	Yes	Core count changes always require a power cycle
Console Type	Yes	VNC/Spice/Serial changes take effect on next power on
Video Card	Yes	Video adapter changes require power cycle
Machine Type	Yes	Chipset changes require power cycle
UEFI/BIOS	Yes	Boot mode changes require power cycle

Hot-Plug Requirements

For drive and NIC hot-plug to work:

1. Allow Hotplug must be enabled on the VM (this is the default)
2. The guest operating system must support hot-plug for the device type
3. For drives, using the Virtio-SCSI interface provides the best hot-plug compatibility

Performing Hot-Plug Operations

Adding a drive or NIC while VM is running:

1. Navigate to the VM dashboard
2. Click Drives or NICs on the left menu
3. Click New to add the device
4. The device appears in the guest OS (may require a rescan in some operating systems)

Removing a drive or NIC while VM is running:

1. Navigate to the VM dashboard
2. Click Drives or NICs on the left menu
3. Select the device to remove
4. Click Hotplug on the left menu to safely detach it
5. Once detached, the device can be deleted

Guest OS Considerations

Before hot-removing a drive, ensure it is not in use by the guest OS. Unmount filesystems and remove from any volume groups or RAID arrays first.

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Tenant Node Resources

Tenant nodes behave differently from VMs regarding resource changes.

Tenant Resources Can Be Changed Live

Resource	Live Change	Notes
RAM	Yes	Tenant node memory can be increased or decreased without restart
CPU Cores	Yes	Tenant node cores can be increased or decreased without restart
Storage	Yes	Storage tiers can be added or expanded without restart

Tenant nodes are designed for flexible resource allocation. You can adjust a tenant node's RAM and cores from the parent system without interrupting workloads running inside the tenant.

How to Modify Tenant Node Resources

1. From the tenant dashboard, click Nodes on the left menu
2. Double-click the tenant node to modify
3. Click Edit on the left menu
4. Adjust Cores and/or RAM as needed
5. Click Submit

The changes take effect immediately without requiring the tenant or its workloads to restart.

Resource Planning

While tenant node resources can be changed on the fly, the resources must actually be available on the physical host. The system validates availability when the change is submitted.

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Summary

Component	RAM	CPU	Drives	NICs
VM	Power cycle	Power cycle	Hot-plug	Hot-plug
Tenant Node	Live change	Live change	N/A	N/A

For VMs, plan RAM and CPU requirements before powering on, as changes require a power cycle. Drives and NICs can be adjusted on the fly.

For tenants, resources can be adjusted at any time without service interruption, making it easy to scale tenant environments as needs change.