What is the best way to add NVMe M.2 SSD to a VM via "qm set" command or by adding a PCIe device in GUI's VM Hardware page?

[rigel.local]

I need to passthrough NVMe M.2 SSDs to a TrueNAS VM and found out 2 Options:

1. I can simply use Proxmox GUI and add a PCIe M.2 device on Hardware page:



2. Or it is possible to add NVMe device as "hard disk" using this command:

qm set 110 -virtio1 /dev/disk/by-id/nvme-SAMSUNG_MZ1LB1T9HALS-000FB_SERIALNUMBER


What is the difference between these 2 methods when it comes to performance and stable work within VM?

After I add 4 NVMe drives via Hardware GUI it looks like this:


and after I add them via qm set command it looks like this:

(device serial numbers have been blurred)

 

[noel.]

Hi,

The core difference is, that in 1. you are passing through the entire PCIe device [1][2] whereas in 2. the drives are handled by virtio [3].
That means with 1. you are directly giving the vm hardware whereas in 2. you have a layer of abstraction (by the virtio drivers) that then pass the disk from the host to the vm.
My educated guess would be that 1. gives better performance. However, you won't be able to use the snapshot feature or make backups with Proxmox Backup Server [4] , since Proxmox VE will have no idea that the passed-through device is a storage device. So you will have to backup using a different method.

Useful links for you could be the docs [5], our wiki on performance tweaks [6] and our wiki on how to benchmark storage speeds [7]

---

[1]: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#qm_pci_passthrough
[2]: https://pve.proxmox.com/wiki/PCI_Passthrough
[3]: https://developer.ibm.com/articles/l-virtio/
[4]: https://pbs.proxmox.com/docs/
[5]: https://pve.proxmox.com/pve-docs/pve-admin-guide.html
[6]: https://pve.proxmox.com/wiki/Performance_Tweaks
[7]: https://pve.proxmox.com/wiki/Benchmarking_Storage

 

[rigel.local]

Thank you so much for your explanation and useful links for further reading on the subject! It looks like PCIe device passthrough is more suitable option for me.