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Hi Andreas,</div>
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I have done some more testing in a virtualized environment. I took AlmaLinux 8.10, fully updated (kernel 4.18.0-553.74.1.el8_10.x86_64) and build zfs 2.1.16 and lustre 2.15.6 + 2.15.7</div>
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For lustre 2.15.6 compression works as expected. (see attached file)</div>
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For lustre 2.15.7, depending on the PFL layout, there is some compression, but less than with 2.15.6. Or there is no compression on the OST's at all.</div>
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In the test where there is some compression, the PFL layout is simple, few components and no SEL.</div>
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I have also tested lustre 2.15.5 on AlmaLinux 8.6, self compiled, and that also worked as it should.</div>
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In my previous test with AlmaLinux 8.10 - Lustre 2.15.5 - ZFS 2.1.15, compression did not work. That was on bare metal, where zfs was installed from the zfsonlinux repo. Lustre was installed from the whamcloud repo.</div>
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No idea what can cause this, but there seems to be something not ok with lustre 2.15.7 in combination with zfs compression.</div>
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Best regards,</div>
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Martin Balvers</div>
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<span style="font-family: Calibri, sans-serif; font-size: 12pt; color: black;"><b>Danone Global Research & Innovation Center B.V.</b></span></p>
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<span style="font-family: Calibri, sans-serif; font-size: 12pt; color: black;">Uppsalalaan 12, 3584CT Utrecht</span></p>
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<b>From:</b> Andreas Dilger <adilger@ddn.com><br>
<b>Sent:</b> Friday, August 01, 2025 22:58<br>
<b>To:</b> BALVERS Martin <Martin.BALVERS@danone.com><br>
<b>Cc:</b> lustre-discuss <lustre-discuss@lists.lustre.org><br>
<b>Subject:</b> Re: [lustre-discuss] No ZFS compression on OST's when using PFL </div>
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<div style="line-height: 1; font-size: 11px;"><b>WARNING - EXTERNAL SENDER - BE CYBERSAFE</b></div>
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<div>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 data-issue-key="LU-19193" data-auth="NotApplicable" rel="91120" class="OWAAutoLink" id="OWAa0ffed96-edf0-791a-c709-ac2d3a887e89" href="https://urldefense.com/v3/__https://jira.whamcloud.com/browse/LU-19193__;!!OUGTln_Lrg!Ugs-QNv1jVaQ0FZzMnQ9mLWiu0QW-B3iSDiiXoIU2XwGrg2ab0Uh-J-krG6w9pYI3ffwwwLgjxtjhLeNfA$">
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 style="direction: ltr; text-indent: 0px; color: black;">Cheers, Andreas</div>
<div style="direction: ltr; text-indent: 0px; color: black;">—</div>
<div style="direction: ltr; text-indent: 0px; color: black;">Andreas Dilger</div>
<div style="direction: ltr; text-indent: 0px; color: black;">Lustre Principal Architect</div>
<div style="direction: ltr; text-indent: 0px; color: black;">Whamcloud/DDN</div>
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