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I have been running zfs on root in ubuntu 18.04 and recently did a release-upgrade to 22.04. With it, zfs was upgraded from 0.8.something to 2.1.4.

Now, my zpool on the laptop prominently informs me about zpool upgrade:

generic@motorbrot:/tmp$ sudo zpool status tank -v
  pool: tank
 state: ONLINE
status: Some supported and requested features are not enabled on the pool.
    The pool can still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
    the pool may no longer be accessible by software that does not support
    the features. See zpool-features(7) for details.
  scan: scrub repaired 0B in 00:29:29 with 0 errors on Mon Feb 13 17:24:37 2023
config:

    NAME         STATE     READ WRITE CKSUM
    tank         ONLINE       0     0     0
      nvme0n1p9  ONLINE       0     0     0

errors: No known data errors

Why would I want to do this, in the scenario of simple consumer use-cases?

I am aware that it has to do with some features (that can be listed with zpool get all tank | grep feature@) but the list of features is not self-explanatory. Hence I am wondering whether I should heed the warning or better ignore it.

In favor of simply doing nothing:

  • I do not want to break access to the pool. Chances of this happening are small though, unless I'd downgrade my zfs version again.

  • I also do not want to break backing up and it is unclear whether backing up from an upgraded pool to an old pool would still work.

  • This github issue

    The whole problem of this message in the first place is it encourages the user to perform a completely unnecessary pool upgrade, putting the pool at risk and limiting compatibility. Users should be taught to be conservative and only perform upgrades if they really want or need a new feature. "If it ain't broke, don't fix it."

It is apparently possible to disable the warning:

Fortunately OpenZFS 2.1.0 provides a feature that lets you shut this up, in the form of OpenZFS's support for partial upgrades. If you set the new 'compatibility' property to what you already have, 'zpool status' won't nag you (although 'zpool upgrade -v' will show you what you're missing).

So all things considered, do I want to upgrade the zpool without explicitly being aware of a newer feature that I'd need? Or should I ignore the warning? Perhaps even better, can I turn it off somehow so that it would only show up once there is actually a missing feature?

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  • 2
    Why guess? Just check which new features are available, research what they do (not just the name) and then decide. Thanks to feature flags, you don’t have to enable all features at once either but can enable them selectively.
    – Daniel B
    Commented Feb 13, 2023 at 17:08
  • 1
    @DanielB because researching all feature flags sounds like lots of effort that could potentially be for absolutely nothing. I was hoping there is a simpler answer like "most features don't really matter, here is the single important one"
    – lucidbrot
    Commented Feb 13, 2023 at 17:10
  • 4
    But how could we tell which features are important for you? “Simple consumer use-cases” is an awfully broad description of what is happening on the system. Are you only adding files? Are you deleting files? Do you use snapshots? Do you use encryption? Do you have virtual machines’ virtual disks on the filesystem? There are simply too many variables in this regard, especially for the Stack Exchange Q/A format.
    – Daniel B
    Commented Feb 13, 2023 at 17:12
  • Hmm you have a point @DanielB ... but at the same time, it does not seem like there is clear guidance anywhere on what could go wrong with a pool upgrade, how to recover if it does break something, how to decide whether to upgrade in the first place etc. Not sure how to ask the question less broadly
    – lucidbrot
    Commented Feb 13, 2023 at 17:15
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    There is. Not a new "issue" by any strech of the imagination. bbs.archlinux.org/viewtopic.php?pid=1859136#p1859136 <- This provide a nice summary.
    – ChanganAuto
    Commented Feb 13, 2023 at 17:18

1 Answer 1

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There's clearly one (irresponsible) answer here... YOLO.

WARNING: Not responsible for any inaccessible zpools. It would be better to research each feature first, but who has time for that. If you do choose this ill-advised advice, please back-up your data first.

sudo zpool upgrade tank

PS: I did this and didn't have any issue accessing my drives.

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