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You are changing a number of different things with each of your tests, not just Lustre. It could be ZFS 2.1.5->2.1.15 or Alma 8.6->8.10 is also causing issues... Hard to say for sure without apples-to-apples comparisons.
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<div>It should be possible to build Lustre 2.15.5 on Alma 8.6 + ZFS 2.1.5 to help isolate the issue.</div>
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<div>There was <a class="issue-link" data-issue-key="LU-19193" href="https://jira.whamcloud.com/browse/LU-19193" id="key-val" rel="91120">LU-19193</a> filed recently about ZFS and blocksize detection, which might hurt ZFS compression, but that was never landed
on 2.15.</div>
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<div>Cheers, Andreas<br>
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<div>On Aug 1, 2025, at 06:33, BALVERS Martin via lustre-discuss <lustre-discuss@lists.lustre.org> wrote:</div>
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I ended up installing lustre 2.15.1 on the new servers. Now compression works as expected when PFL is enabled.</div>
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What I have tested so far is:</div>
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AlmaLinux 9.4 - Lustre 2.16.1 - ZFS 2.1.16 - No compression with PFL</div>
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AlmaLinux 8.10 - Lustre 2.15.7 - ZFS 2.2.8 - No compression with PFL</div>
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AlmaLinux 8.10 - Lustre 2.15.5 - ZFS 2.1.15 - No compression with PFL</div>
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AlmaLinux 8.6 - Lustre 2.15.1 - ZFS 2.1.5 - PFL + compression works as expected</div>
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I tried installing 2.15.2, 2.15.3 and 2.15.4 but that failed with ksym errors.</div>
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It seems that somewhere between lustre 2.15.1 and 2.15.5 the PFL + compression breaks.</div>
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gr,</div>
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Martin Balvers</div>
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<div>Cheers, Andreas</div>
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<div>Andreas Dilger</div>
<div>Lustre Principal Architect</div>
<div>Whamcloud/DDN</div>
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