Moving a FreeNAS ZFS Pool from a Physical Server to a VM using RDMs

I’ve been using FreeNAS for several years now for both block and NFS storage in my home lab with great success. For more information on my most recent FreeNAS build, you can check out the series here.

Although I’ve been quite pleased with this setup, I had to repurpose the SSDs in the box and had yet another USB boot device failure. This meant I had to reinstall FreeNAS and left me with just a single ZFS pool with a pair of 2TB mechanical drives. It just didn’t feel right to have a full system up and running for just a pair of 2TB drives when I could run them just fine in my management ESXi host. Not to mention the fact that I’ve got 224GB of RAM available there to provide for a much larger L1 ARC cache.

In part 2 of my FreeNAS build series, I looked at using VT-d to passthrough a proper LSI SAS HBA to a VM. This is really the best possible virtual FreeNAS configuration as it bypasses all of the hypervisor’s storage stack and grants direct access to the HBA and drives. I considered using this setup, but I didn’t think it was worth the extra power consumption and cooling needed for the toasty PERC H200 card I’ve been using. Since I wanted to preserve all data on the drives, RDMs seemed to be the next logical solution. This isn’t as ‘pure’ as the VT-d solution, but it still gives the VM full block access to the drives in the system. At any rate, it was worth a try!

Disclaimer: If you are using ZFS and FreeNAS for production purposes or for any critical data that you care about, using a proper physical setup is important. I wouldn’t recommend virtualizing FreeNAS or any other ZFS based storage system for anything but testing or lab purposes.

What I hoped to do was the following:

  1. Take the 2x2TB Western Digital hard drives out of the Dell T110.
  2. Re-install the 2x2TB drives in my Intel S2600 management host on the integrated SATA controller.
  3. Create a new FreeNAS virtual machine.
  4. Add the two drives to the VM as virtual mode RDMs.
  5. Import the existing ZFS volume that is striped across these two drives in FreeNAS.
  6. Re-create the iSCSI target and NFS shares and have access to all existing data in the pool! (assuming all goes well).

Creating a new FreeNAS VM

Once I got the two drives installed in my Intel S2600 management host, I created a new VM and got the FreeNAS OS installed. Below is the virtual hardware configuration I used:

Guest OS type: Other, FreeBSD 64-bit
CPUs: 2x vCPUs
Memory: 16GB (a minimum of 8GB is required)
Hard Disk: 16GB (for the FreeNAS OS boot device, a minimum of 8GB is required)
New SCSI controller: LSI Logic SAS
Network adapter type: VMXNET3
CD/DVD Drive: Mount the FreeNAS 11.2 ISO from a datastore

You’ll notice that some of the options I selected are not defaults for FreeBSD based VMs. This includes the LSI SAS adapter, and the VMware VMXNET3 NIC. LSI Parallel is the default for FreeBSD VMs, but the SAS adapter works well with all recent BSD builds. The same holds true for the VMXNET3 adapter, which has many benefits over the emulated E1000 adapter type.

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