May 20, 2022

Freenas Cache Drive

Running Many Virtual machines can be demanding on A physical hard drive. My plan was simple, add a cache drive for the virtual hard disk pool on my Freenas. well, did it work?

The idea comes from being concern about the performance of my VM’s running on Freenas. My thought was if there’s a way to improve the performance., it would save me time and my sanity. I remember Freenas had the ability to cache storage pools using drives as cache. I knew that an SSD would be a good option, but didn’t have any available drive ports to install on on the workstation. Then when looking around at prices on SSD’s, I saw Intel Optane 16GB drive for around $10. Then I came up with my grand plan “why not get a m.2 card and this and install it? it should defiantly be faster!” I was curious so I order it to experiment to see if Intel Optane, will improve my performance.

My setup for FreeNAS is quite unique. It runs on a virtual machine, And the hard drive controller pass to it. To make the Intel Optane visible to my Virtual Machine is do the same as the Hard Drive Controller. (note this isn’t a tutorial on how to setup passthrough on a virtual server)

It was pretty obvious which one was the NVME drive(hint it’s the one without a description). But to be sure I did a quick check with lspci command on the VM server.

Non-Volatile memory? sounds like winner to me.

A quick search on the internet revealed Device 2522 which is an Intel Optane drive. And that’s all I needed to know, Now to do is add it to the VM and reset the server. (The server needed to reset so the device can be freed for the Hypervisor to use it.)

Now I Setup the Pool to use the cache drive I added.

Navigating to storage/pools then selecting extend on the Virtual Machine pool.
Click Add cache
I check the Optane drive then hit the arrow
Then I hit extend to apply the new cache to the pool and confirm it.

So did it work? well, that will be in the next part when I give some benchmarks out.

(Update as of 3 july 2021)

Unfortunately, I didn’t record the benchmarks but, The Performance I got wasn’t noticeable or remarkable. I believe that the cache drive wasn’t big enough to make a difference. Once I get a bigger NVME drive I try it again.


Computer guru with years working with technology. I find it fun to tinker with computer new and old, and make them do my work for me.

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