How safe is to upgrade ZFS pool?

[idgar]

Hi,
1. how safe is to upgrade ZFS pool?
2. is it prone to errors in certain cases?
3. is it upgrading the filesystem disk by disk?
4. how much time it can take?

 

[jgreco]

1) Should be completely safe. However, you will not be able to UNDO it, so typically those of us who do lots of ZFS will wait to upgrade, a month, a year, or, my favorite, right BEFORE upgrading to a new version of FreeNAS/TrueNAS. This counterintuitive strategy guarantees that you're introducing new feature flags and aren't stuck on a pool version from ten years ago, but also guarantees that you can roll back from your about-to-be-installed version to the version currently running.

2) Shouldn't be.

3) No.

4) Perhaps a second. Maybe two.