Templates and VM Cloning Fails with iSCSI Configuration

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sethgreenfield

New Member
Jan 14, 2026
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Hey All,

I currently have 5 Proxmox 9 servers clustered and working well. I'm using a TrueNAS M40 for Block Storage via iSCSI. I cannot successfully get templates to clone off of, or successfully clone a VM. VMs are running fine. Hiccup we've encountered is that the zvol needs to be 4k or less and the extent on iSCSI as Legacy OS (512 Block Size) for templates/cloning to work. I've tried a number of other combinations with no luck. Something I saw said that the block size for the zvol needs to be 16 or 64. If I do less then 32k, I lose out on a storage cap. I also loose out on IOPS and other beneficial stuff when lowering.... Does anyone know of alternatives to get the templates to function? Current plan is to leverage a separate server to host them, then deploy a clone there, back it up, and send that backup to the cluster for use.
 
In my own efforts I've found that CLI cloning works. Proxmox GUI clone feature zeros a disk before cloning occurs, this is causing the issue. I'm going to see if I can find any config files to modify this feature out.
 
We're using LVM over LUN. We want thick provisioning for this configuration. I've tried digging into some of the pearl code to manually change this, no success. I forgot to mention, executing the same exact qemu-img clone command via the CLI works. It's just the disk zeroing prior that doesn't go well with the 32k and 4k block size configuration set, and that's what the GUI full clone does
 
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