Upgrade ZFS boot pool to new features

[djf_jeff]

I have upgraded to the latest TrueNAS-12.0-U8.1. I was wondering if I can upgrade the zpool freenas-boot to the latest ZFS features.

I know this is something we don't normally recommend as I saw in other threads here. There is a possibility that the bootloader won't be able to see the pool on the next reboot.

however, I was wondering if it is safe to upgrade with this release? Does the bootloader in 12.0-U8.1 will see the latest ZFS features on the pool on the next reboot?

The reason I ask is because this boot pool was created a very long time ago (9.3 if I recall correctly) and I would like to make it a little more actual. If I were to install 12.0 as a clean install today, I guess the boot pool would have the new features enabled, right?

Thanks!

 

[Nick2253]

Having the new features doesn't really help you, unless you actually need those features. In fact, keeping the pool as "old" as possible is generally a benefit, because that maximizes compatibility.

 

[djf_jeff]

I understand but as I said in my original post, I just want to experiment and understand this part.

Is there a way to check at what version my ZFS features are?

 

[Jailer]

You can experiment if you want, just make sure you have a backup of your configuration before you do the pool upgrade. Having said that as you previously stated there are many posts out there by others, much more knowledgeable than me, that have said it's not wise to upgrade the boot pool. @Ericloewe is one who has posted the most on this and maybe he can shed a bit more light on it before you possibly step into a completely avoidable troublesome situation.

 

[Ericloewe]

Is there a way to check at what version my ZFS features are?

Your terminology is incorrect, and that is not me just being a pedant, it's an important distinction: Feature Flags can be disabled, active or enabled. See the resource for more details (TrueNAS 13 adds draid, haven't had the time to update the resource yet):

ZFS Feature Flags in TrueNAS

OpenZFS' distributed development led to the introduction of Feature Flags. Instead of incrementing version numbers, support for OpenZFS features is indicated by Feature Flags. Feature Flag states Feature flags exist in one of three states...

www.truenas.com

As for upgrading boot pools: You really should not without a very good reason.

The reason I ask is because this boot pool was created a very long time ago (9.3 if I recall correctly) and I would like to make it a little more actual.

Well, thing is, I don't think any Feature Flag after 9.3 has meaningful benefits for a boot pool.

Does the bootloader in 12.0-U8.1 will see the latest ZFS features on the pool on the next reboot?

The question isn't as much "does the bootloader support it", because the FreeBSD bootloader generally is in sync with ZFS - aside from edge cases like encryption and draid, which take longer and/or are unlikely to be relevant for a boot pool. The question is: was the bootloader correctly updated on-disk?
There was a thread about that recently, but I don't have a link to it. The short version is that this process is not always flawless.

So, high risk and zero reward make for a less-than-popular procedure.