Attempting to install TrueNAS VM on Proxmox, trouble with RAID controller passthrough


New Member
Oct 17, 2023
Hello everyone, I should start by saying that I'm very new to Linux and virtualization so I'm sorry if this is a really dumb problem. Essentially, I am trying to install a TrueNAS VM on Proxmox, that part went relatively smoothly. My server has a hardware RAID controller (shows up in PCI devices as "MegaRAID SAS 2208 [Thunderbolt]") and I want to passthrough that device to TrueNAS. I was able to create a virtual drive in Proxmox and pass that through to TrueNAS, that seemed to show up properly (though had some issues with permissions, unrelated). However after some reading, I am a little worried that this configuration could cause problems down the line that I won't easily be able to solve. So I figured I would passthrough the entire controller and let TrueNAS manage the whole thing. Problem is, when I add the device to TrueNAS in Proxmox, I am unable to then create a pool on it in TrueNAS because the physical drive doesn't show up like the virtual drive did.

The first issue I had was with IOMMU, which was not allowing me to add the controller to the TrueNAS VM, this was fixed by adding "GRUB_CMDLINE_LINUX_DEFAULT="intel_iommu=on"" to /etc/default/grub. I'm now able to add the device, but its worth noting that there is nothing in the "Mapped Devices" dropdown, all devices are found under "Raw Devices." However, booting into TrueNAS does not show any drives on which to create a pool.

At this point I'm not really sure where to go. I'm happy to provide any additional details or logfiles anyone needs (though I might help finding those logfiles). My server is from Supermicro, I'll have to look for the model number. The processor is an Intel Xeon E3-1240. BIOS was last updated in 2014, but I did confirm that the virtualization features are enabled. The PCI Passthrough documentation also mentioned a feature called ACS which could separate all PCI devices onto their own IOMMU groups (I did notice that all of the PCI slots are on the same group, maybe related?) but I could not find this feature in my BIOS. I saw there was a *risky* workaround patch, but I don't want to mess with that unless I'm sure it's related.

That's all I have for now, please let me know if you need any more information. And thanks in advance for looking this over!


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