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Overview

Live vCPU and RAM scaling lets you adjust the compute resources of a running instance without rebooting. Changes take effect immediately while the instance continues serving traffic.
Xloud-Developed — Live vCPU/RAM Scaling is developed by Xloud and ships with XAVS / XPCI.
Prerequisites
  • Instance must be in ACTIVE state
  • The flavor must have live scaling enabled by your administrator — if you do not see the Live vCPU/RAM button, contact your admin

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Scale vCPU or RAM from the Dashboard

Open instance actions

Navigate to Project > Compute > Instances. Find your instance and open the Actions dropdown.

Select Live vCPU/RAM

Click Live vCPU/RAM from the dropdown. A dialog opens showing current and allowed values:
FieldDescription
Current vCPUsHow many vCPUs the instance has right now
Desired vCPUsEnter the new vCPU count
Current RAM (MB)Current memory allocation
Desired RAM (MB)Enter the new RAM value

Apply the change

Enter the new values and click Apply. The change takes effect immediately — no reboot, no confirmation step.
Scaling down RAM while applications are using it may cause out-of-memory events inside the guest. Check application memory usage before reducing RAM.

Verify inside the instance

SSH into the instance and confirm the new resources:
Check vCPU count
lscpu | grep "^CPU(s):"
Check available RAM
free -h
The guest OS shows the updated vCPU count and memory — live scaling applied successfully with zero downtime.

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Comparison: Live Scaling vs. Flavor Resize

Live vCPU/RAM ScalingFlavor Resize
DowntimeNone — instance stays runningReboot required
ScopevCPU and RAM onlyvCPU, RAM, and disk
DirectionUp or down within envelopeUp or down (disk: up only)
Confirmation stepNo — instantYes — must confirm or revert
Use caseResponding to live load changesPermanent tier change

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Troubleshooting

The instance’s flavor does not have live scaling enabled. Contact your administrator to configure the flavor with hot-add extra specs.
The requested value is outside the allowed range configured on the flavor. Try a smaller value, or ask your admin to increase the flavor’s scaling limits.
On older Linux kernels (before 4.15), new CPUs may need to be brought online manually:
Bring hotplugged CPUs online
for cpu in /sys/devices/system/cpu/cpu*/online; do echo 1 > $cpu; done
Modern kernels (4.15+) bring CPUs online automatically.
The guest OS memory balloon driver may not be loaded. Check inside the guest:
Check balloon driver
lsmod | grep virtio_balloon
If not loaded: modprobe virtio_balloon and add virtio_balloon to /etc/modules for persistence.

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Next Steps

Admin: Enable Live Scaling

Configure flavors with hot-add extra specs, resource bounds, and NUMA settings

Resize Instance

Standard flavor resize — change vCPU, RAM, and disk with a reboot

Advanced Features

CPU pinning, NUMA topology, huge pages, and vTPM

Compute User Guide

Overview of all compute instance operations