Support for new features from ZoL 0.7

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Support for new features from ZoL 0.7

Postby RJVB » Sun Nov 19, 2017 3:13 am

Hi,


Side-ways related to viewtopic.php?f=24&t=3077:

Is any form of ("as-far-as-possible") support planned for the new features in ZFSonLinux 0.7.x? I just saw this:

Code: Select all
> zpool import -d /dev
Password:
   pool: bolaLNXBak
     id: 15783517359236047261
  state: UNAVAIL
status: The pool uses the following feature(s) not supported on this sytem:
        org.zfsonlinux:large_dnode
        org.zfsonlinux:userobj_accounting
action: The pool cannot be imported. Access the pool on a system that supports
        the required feature(s), or recreate the pool from backup.
 config:

        bolaLNXBak  UNAVAIL  unsupported feature(s)
          disk1s6   ONLINE


I did experiment with setting `dnodesize=auto` on some of that pool's datasets but I didn't touch the userobj_accounting feature (not voluntarily/explicitly at least). The pool imported just fine until I upgraded it.

If I interpret this correctly, O3X isn't currently able to import pools created with the current stable ZoL release (v0.7.3), and that seems like more than just a bummer.
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Re: Support for new features from ZoL 0.7

Postby lundman » Sun Nov 19, 2017 4:25 pm

You can create a pool without those features of course. When I ported over largednode to OSX, back when it was new, it did very poorly, corrupted the test pool. So I never included it in master, figured I would wait for ZOL to iron out the issues, and PR it to OpenZFS repo. This is what we are waiting on still.

I have not tried the userobj accounting commit yet (not in openzfs either) as it didn't sound very interesting :)
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Re: Support for new features from ZoL 0.7

Postby RJVB » Sun Nov 19, 2017 5:23 pm

I don't know if one can still create pools without the new features, but you clearly can't do `pool upgrade` without activating the the userobjc_accounting one. And that one cannot be disabled afterwards, apparently. Once active pools can only be imported read-only. I agree it doesn't sound very interesting, but if I understand its purpose correctly it should be possible to implement it on Darwin too (at least in such a way that the existing accounting information is preserved).

As to the dnode feature: that one goes back to a compatible state once the last dataset that ever had a non-legacy dnodesize attribute is destroyed. A bit drastic but at least there's some kind of workaround. I asked about the feature on IRC and didn't get any reaction suggesting there are known reasons to avoid it. The only advice was not to touch it unless you have a good reason - no good reasons were given. I haven't found any either, at least not in the form of a noticeable disk I/O performance gain in my regular workload. Either way, might be worth it to have another look if you still know your way around that code.
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Re: Support for new features from ZoL 0.7

Postby lundman » Sun Nov 19, 2017 10:22 pm

On large-dnodes, the PR to keep an eye on: https://github.com/openzfs/openzfs/pull/409
and note that brian point out a bunch of bug fixes near the end, but I don't know if they've included those yet.
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Re: Support for new features from ZoL 0.7

Postby RJVB » Mon Nov 20, 2017 1:41 am

Of the 3 bug Brian mentioned:

PR #6564 was merged into master on Sept. 6th
PR #6396 was merged into master on July 26th
PR #6576 was also merged into master on Sept. 6th but apparently has side-effects with #6564

I don't see any explicit mention of either having been included in a 0.7 release version, esp. not for #6396 .
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Re: Support for new features from ZoL 0.7

Postby lundman » Mon Nov 20, 2017 2:35 am

Heh - I mean, we need to make sure they are in the OpenZFS PR ... that is what we pull in if Ahrens approves it
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Re: Support for new features from ZoL 0.7

Postby RJVB » Mon Nov 20, 2017 4:49 am

Ah, right, makes sense.
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