TrueNAS boot drive dilemma : wasted space

alink · April 10, 2025, 12:39am

So I’ve done a bit of searching the web on this topic and have come across threads on Reddit, the TrueNAS forums, etc… but I’d like to ask all of you (the Lawrence Systems community) your opinion regarding TrueNAS boot drives and the space that will often times go to waste.

After double checking the hardware guide it says that 16-32gb is really all that is needed for the boot drive. I’ve been looking at buying an M.2 drive from which to boot TrueNAS, but nowadays even the inexpensive drives can start at 256gb.

Some threads have mentioned partitioning the drive so that part of it can be used as storage.

One possible setup I had in mind for myself would be to have all of my important data in a RaidZ-2 pool of mechanical storage.
On the M.2 drive, I’d partition about 32gb for booting TrueNAS, and then the other partition would be a pool on which I would install Apps. For me, if I lose to M.2 drive due to hardware failure, it’s not that big of a deal as long as my RaidZ-2 pool data is safe.

I’d like to hear what you all think though. Do you prefer to use the boot drive solely for that purpose? Or do any of you dabble with partitioning the extra space? Any pros and cons you can offer?

Louie1961 · April 10, 2025, 2:27am

You can use the boot drive to store your IX volumes for docker. No special partitioning required.

LTS_Tom · April 10, 2025, 10:35am

That is not true, it does not allow you to choose the boot pool.

My preferences is to use an older pair of SSD’s as a boot drive and not worry too much about the wasted space. While officially not supported you can use the extra space of the boot drive for other purposes but that does increase the complexity.

Louie1961 · April 10, 2025, 11:57am

OK, then I am confused. What is this setting?

xMAXIMUSx · April 10, 2025, 12:37pm

I’m with @LTS_Tom. Who cares about the extra space on a boot drive. It should only serve for a single purpose. You wouldn’t want to be wearing out the drives faster because you are concerned about space you want to use on them.

LTS_Tom · April 10, 2025, 6:03pm

That is for the System Dataset Pool where the logs go.

das1996 · April 12, 2025, 5:46am

gist.github.com

https://gist.github.com/gangefors/2029e26501601a99c501599f5b100aa6

Install FreeNAS SCALE on a partition and create a mirror.md

# Install TrueNAS SCALE on a partition instead of the full disk

The TrueNAS installer doesn't have a way to use anything less than the
full device. This is usually a waste of resources when installing to a
modern NVMe which is usually several hundred of GB. TrueNAS SCALE will
use only a few GB for its system files so installing to a 16GB partition
would be helpful.

The easiest way to solve this is to modify the installer script before
starting the installation process.

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Not for the faint of heart, totally unsupported, ill advised, but doable.

If the drive(s) goes, it all goes, so make sure you have config and data backups.

My use case for this would be a remote nas box using a dell sff case with support for a single 3.5" drive.

edisondotme · April 14, 2025, 8:36pm

I just use two mirrored USB flash drives for the boot pool.
I had a failure one time, replaced it, and it “resilvered” the other flashdrive just fine.