Newbie help: VM Snapshots and Proxmox Node disk format/type

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zulfkar97

New Member
Feb 15, 2025
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Hey! I come from a Windows/VMware environment. Switching to proxmox for VMs and especially LXC.

I have 2 new Proxmox VE 8.3.0 nodes. Each has exact same hardware & both have a 256GB nvme (for Proxmox install) and a WD Red 2TB SSD (for VMs, CTs etc).
ISOs are accessed via NFS share from a QNAP NAS.

I've setup a few VMs when I came across the inability to Snapshot "current guest config does not support snapshots". Seems in both nodes the 2TB disks were added as /dev/sda and as LVM. I'm assuming, from what I've read, the VM disk(s) should be in qcow2 format and not RAW. The problem is, in the VM creation wizard when I select the 2TB disk as target for Virtual Disks the option to select qcow2 is greyed out and defaults to RAW.

Is this related to how I have setup the 2TB disk within the node, have I added the disks in incorrectly or missed out on a step? If so it possible to resolve this without deleting the VMs I have already setup on both nodes?

I've gone through the official documentation and searched this forum, although options & info about file systems are given (LVM vs ZFS etc.) very little is shown on the implemention side. Also yes, I'm new to Linux! Running df -h in the shell fails to show the 2TB SSD as part of the configured filesystem but it does show via fdisk -l!
Screenshot 2025-02-22 223336.png
 
You configed your 2TB ssd as lvm and without a filesystem so it isn't shown by df. See output of cmd's pvs, lvs, lvdisplay.
Normally you should be able to covert your vm disk if you want to by select your vm (stopped), select hardware, select disk, select Disk Action, select Move Storage, select same target, select your desired format, eg qcow2, select blue move storage.
 
waltar said:
You configed your 2TB ssd as lvm and without a filesystem so it isn't shown by df. See output of cmd's pvs, lvs, lvdisplay.
Normally you should be able to covert your vm disk if you want to by select your vm (stopped), select hardware, select disk, select Disk Action, select Move Storage, select same target, select your desired format, eg qcow2, select blue move storage.
Click to expand...
Thanks, so it seems using the same storage (the 2TB SSD) I cannot move disks, option to change from RAW to qcow2 is not available:

Move Storage Screenshot 2025-02-23 144237.png
 
From what you say it seems I have to define a filesystem for the LVM volume - how do I do this & is this destructive to the VM disks already configured on that physical disk?
 
When you take a look to "lvs" output and the see the "data" volume you see the "t" for lvm-"t"hin out of the volume group "pve".
You have done a volume group "vms" on your 2TB ssd but not definded a thin volume before defining your 4 vm-100 disk into and so you have 4 lvm-thick volumes which doesn't allow you in pve the snapshots.
a) When you again try to "move" your 4 vm-disks into "pve" first, then define a lvm-thin volume (eg vms also or vmst) and then "move" back you should be able to do snapshots.
b) When you want a filesystem on your 2TB ssd, again "move" your 4 vm-disks into vg "pve" first, delete vg and pv by "vgremove vms" and "pvremove /dev/sda" and than eg. "mkfs.<xfs|ext4> /dev/sda" which then could be mounted eg under /vms, define in datacenter with storage "dir" after nad "move" your 4 vm-disks back.
Anyway you can test both and find a solution which is your desire. I wish you good luck :)
 
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