# GPU FAQs

**Q1. What types of GPU configurations are supported in PCD?**

PCD supports:

* **GPU Passthrough** – Full GPU assigned to a VM
* **vGPU** – Fractional GPU assigned using vendor-defined profiles

***

**Q2. Can a host support both Passthrough and vGPU on the same GPU?**

No. A physical GPU can only operate in **one mode at a time**—either Passthrough or vGPU. <code class="expression">space.vars.product\_acronym</code> blocks conflicting configurations during setup.

***

**Q3. What if the host has multiple GPUs?**

You can configure each GPU on the host independently. Currently, we do not support a combination of multiple GPU modes on a single host. For example, all GPUs on a host can be passthrough or vGPU.

***

**Q4. Can I change the GPU mode of a cluster on VMs are already running?**

No. You must ensure no VM is using the GPU before changing its mode. The system will prevent mode changes if the GPU is actively assigned.

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**Q5. What are vGPU profiles and who defines them?**

vGPU profiles are predefined by NVIDIA. Each profile determines how much GPU memory and what capabilities are given to a VM (e.g., `Nvidia-35`, `Nvidia-40`). Only one profile type can be used per GPU at a time.

***

**Q6. How are GPU-enabled VMs scheduled to GPU hosts?**

GPU-enabled flavors are mapped to GPU-capable host. <code class="expression">space.vars.product\_acronym</code> schedules VMs only to hosts with compatible GPU hardware and profiles.

***

**Q7. Can I migrate a VM with a GPU?**

* **Passthrough GPU:** Live migration is allowed only if the destination host has the same specific physical GPU hardware available.
* **vGPU:** Private Cloud Director (PCD) currently supports vGPU on Ubuntu 22.04 only. The default Ubuntu 22.04 LTS packages do not ship with the required versions of libvirt, QEMU, or the kernel. As a result, vGPU live migration is not supported in PCD at this time.<br>

  Cold migration of vGPU VMs is supported and is the recommended approach when moving a vGPU workload between compute nodes.\
  Live migration of vGPU VMs is supported in Nova ,but requires the following minimum stack versions on both source and destination compute nodes:

  libvirt 8.6.0 or later, QEMU 8.1.0 or later, Linux kernel 5.18.0 or later

***

**Q8. How do I know how much GPU memory is available?**

<code class="expression">space.vars.product\_acronym</code> will display GPU resource availability per host or per host aggregate, including free VRAM. This helps admins plan capacity and allocations.

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**Q9. How do I know what GPU model is on a host?**

GPU Host details in the console will list GPU model, mode (Passthrough/vGPU), available profiles, and current usage.

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**Q10. Can I add a non-GPU host to a GPU cluster?**

No, Currently, <code class="expression">space.vars.product\_acronym</code> does not support it.

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**Q11. Can we passthrough two GPU cards to single VM?**

Yes, you can passthrough two or more GPU cards to single VM by configuring GPU flavor.

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**Q12: Does pausing or suspending a GPU VM automatically release underlying GPUs and re-attach on resuming/power on?**

Currently the GPU are not released and reattached to new GPU VM automatically.

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**Q13: Is VM HA supported for GPU-enabled clusters?**

No, VM HA is currently not supported for GPU-enabled clusters.

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**Q14: Can we over provision GPU passthrough physical PCI resources?**

No, you can not over provision the physical GPU PCI passthrough hardware, unlike CPU,Memory over provision ratios.

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