TrueNAS Migration/ZFS HDD Passthrough


New Member
Dec 31, 2020
Hi, I can't seem to find a definitive answer to this question:
I bought a 500GB replacement boot hard drive that runs my Proxmox VMs because my current one is 256GB and I have run out of space.

My TrueNAS VM has 8 x 4TB drives which are all connected to the VM through passthrough. Is there a way to install Proxmox onto the new boot drive and restore the TrueNAS VM without having to backup and restore the 20TB of data as well? Maybe I could detach the drives temporarily, install Proxmox, restore just the boot drive of the TrueNAS VM and then connect the drives back and manually add the 8 drives back?

I know you can untick the backup option of the 8 drives and just backup the boot VM but would that work? Or will I break something in the process and lose all my data? Thanks.
Are you using LVM-Thin or ZFS for your boot disk?
Its also an option to clone the whole old disk to the new one but then you would have to manually extend your partitions, pools, LVs, filesystems and so on which isn't that easy.

When excluding disks from backup you will have to be careful. PVE will destroy the complete VM with all virtual disks while doing a restore. This will also destroy excluded virtual disks (LVs/zvols). But if I remember right restoring a VM with disks passthroughed (like described here) it will only remove the passthroughed disks from the config file but will keep the disks untouched and won‘t format them so they could be readded later.
But you better test that yourself first.
Hi Dunuin, the disks that are booted from are LVM-Thin but the data in TrueNAS is in ZFS. There might not be an update on this one for another week or so because I had two ideas:
I could 1. Wing it. Do a fresh install of Proxmox, restore the TrueNAS VM, re-attach the drives through passthrough. So while it doesn't technically scrub anything because I'm only leaving drives out of backup, there shouldn't be a problem AND if something does go awry, I can just go back to the original boot drive with the original config (because the drive is being entirely upgraded, not wiped and start again) OR
2. Do an entire backup of the whole thing to a NAS I can borrow from work which will take a considerable amount of time but ensure that if anything goes horribly wrong, the data is still all there. And I'm leaning towards number 2.

Edit: I'll still keep a watchful eye in case anyone else posts a test and it was successful.
Just a thought - could you just add the 500GB drive and migrate your VM's onto it?
Hi Bob, my motherboard has 2 x m.2 slots. However, if I am using all 6 SATA connectors (which I am), the second m.2 slot doesn't work - it's a shortcoming of the board and I am guessing the chipset.

Not to worry though, because I did it last night with absolutely no problems! I swapped out the m.2 boot drive, installed latest version of Proxmox and TrueNAS recognized the RAID but had to manually passthrough the drives again through shell. Glad I didn't have to backup the entire dataset or else that could have added another week just in moving that amount of data alone.


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