I just updated my system to 24.10. In the storage dashboard I see an Upgrade button, which may or may not have been there in 24.04, which is the first TrueNAS version I have used. What does that do? Should I upgrade my pool?
OpenZFS indicates support for various ZFS features by setting feature flags on your storage pool. As you upgrade TrueNAS, and thus OpenZFS, additional feature flags may become available. Enabling or activating these new feature flags may make it impossible for your storage pool to be mounted on an earlier version, should you need to roll back TrueNAS or move your pool to another system. Therefore, it’s often recommended to not upgrade your pool with the new flags unless you know you need those features or won’t ever be rolling back.
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More detail on what’s new in OpenZFS 2.3 found in Electric Eel.
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Does that mean it is safe to upgrade if you only have 1 TrueNAS server? I only have one that I just upgraded to EEL 24.10, and I’m determining if it’s better to upgrade or not to upgrade.
I there are no cons, then I’ll update just to be current.
The con is that you can’t switch back to a previous version of TrueNAS, ie Dragonfish.
Upgrading a pool enables all the features that are currently implemented in the current version of ZFS that you are using.
This means you can’t use an earlier version.
You need to be sure that you aren’t going to find a reason to switch back to Dragonfish, for example, if you hit a bug that you can’t wait to be fixed.
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That alone should be a reason to wait until at least .1 or .2 before upgrading.
There’s hardly ever a compelling reason to rush to upgrade storage pools.
And never ever upgrade the boot pool!
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Well, if you want to use raidz expansion you must 
That’s why I wrote “hardly ever” rather than “never”, but the jury is still out on whether jumping on such a new and still potentially risky feature qualifies as " compelling". 
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I did all the upgrades. And I liked it.
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