[SOLVED] Proxmox 7.4-3, Ceph 17.2.5-pve1, cannot create VM with qcow2 format


New Member
Jun 24, 2022
We have a seven node cluster, with three nodes primarily acting as ceph storage servers, and the other four nodes as KVM hosts.
All nodes are running Proxmox 7.4-3. The Ceph nodes run Ceph 17.2.5-pve1.

When I look at the storage pool, all the disk images show up as "raw"

If I try to create a new VM, the disk format option is greyed out (see attached screenshot)

We would really like to be able to use qcow2 where possible, and don't know why we can't.


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    Screenshot from 2023-05-30 11-18-49.png
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You didnt specify what exact storage type you are using in Proxmox. I am guessing its Ceph/RBD.
As you can see here: https://pve.proxmox.com/wiki/Storage , Ceph/RBD is block protocol and so the disk images are raw blocks.
In order to create files (Qcow) you need a file system and for that you need a different/additional storage type - Cephfs.

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox
We would really like to be able to use qcow2 where possible, and don't know why we can't.

can you explain why you think you need qcow2? ceph uses raw, but still provides features like snapshotting, thinprovising etc. nothing to miss regarding features or am I missing something?
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Reactions: bbgeek17
@bbgeek17: Thank you. You're right, we are using raw, and I'd overlooked that qcow can't be used on raw.
@jsterr: I probably misunderstood. I thought that qcow2 had features that default ceph doesn't - but am happy to be mistaken about that.


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