I ended up installing lustre 2.15.1 on the new servers. Now compression works 
as expected when PFL is enabled.

What I have tested so far is:
AlmaLinux 9.4 - Lustre 2.16.1 - ZFS 2.1.16 - No compression with PFL
AlmaLinux 8.10 - Lustre 2.15.7 - ZFS 2.2.8 - No compression with PFL
AlmaLinux 8.10 - Lustre 2.15.5 - ZFS 2.1.15 - No compression with PFL
AlmaLinux 8.6 - Lustre 2.15.1 - ZFS 2.1.5 - PFL + compression works as expected

I tried installing 2.15.2, 2.15.3 and 2.15.4 but that failed with ksym errors.

It seems that somewhere between lustre 2.15.1 and 2.15.5 the PFL + compression 
breaks.

gr,
Martin Balvers

AlmaLinux 8.6 - Lustre 2.15.1 - ZFS 2.1.5

[root@microbio pfl]# ls -lh *
-rw-r--r-- 1 root root 6.3G Jul  1 13:28 test1.txt
-rw-r--r-- 1 root root 6.3G Jul 23 09:34 test2.txt
-rw-r--r-- 1 root root 6.3G Jul 23 09:35 test3.txt

LUSTRE:SVNAME   COMPRESS        NAME     RATIO  REFRATIO   USED  LUSED
lustre-MDT0000  zstd-fast       mdt/mdt  1.51x     1.51x  8.23M  6.80M
lustre-OST0000  zstd            lustre/ost  4.60x     4.60x  1.37G  6.29G
lustre-OST0001  zstd            lustre/ost  4.60x     4.60x  1.37G  6.29G
lustre-OST0002  zstd            lustre/ost  4.60x     4.60x  1.37G  6.29G

[root@microbio pfl]# lfs getstripe test1.txt
test1.txt
  lcm_layout_gen:    40
  lcm_mirror_count:  1
  lcm_entry_count:   5
    lcme_id:             1
    lcme_mirror_id:      0
    lcme_flags:          init
    lcme_extent.e_start: 0
    lcme_extent.e_end:   1048576
      lmm_stripe_count:  0
      lmm_stripe_size:   1048576
      lmm_pattern:       mdt
      lmm_layout_gen:    0
      lmm_stripe_offset: 0

    lcme_id:             2
    lcme_mirror_id:      0
    lcme_flags:          init
    lcme_extent.e_start: 1048576
    lcme_extent.e_end:   134217728
      lmm_stripe_count:  1
      lmm_stripe_size:   4194304
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: 0
      lmm_objects:
      -   0: { l_ost_idx:   0, l_fid: [0x100000000:0x6e:0x0] }

    lcme_id:             3
    lcme_mirror_id:      0
    lcme_flags:          init
    lcme_extent.e_start: 134217728
    lcme_extent.e_end:   2147483648
      lmm_stripe_count:  2
      lmm_stripe_size:   4194304
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: 2
      lmm_objects:
      -   0: { l_ost_idx:   2, l_fid: [0x100020000:0x6e:0x0] }
      -   1: { l_ost_idx:   1, l_fid: [0x100010000:0x6f:0x0] }

    lcme_id:             5
    lcme_mirror_id:      0
    lcme_flags:          init
    lcme_extent.e_start: 2147483648
    lcme_extent.e_end:   6979321856
      lmm_stripe_count:  3
      lmm_stripe_size:   4194304
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: 2
      lmm_objects:
      -   0: { l_ost_idx:   2, l_fid: [0x100020000:0x6f:0x0] }
      -   1: { l_ost_idx:   1, l_fid: [0x100010000:0x70:0x0] }
      -   2: { l_ost_idx:   0, l_fid: [0x100000000:0x6f:0x0] }

    lcme_id:             6
    lcme_mirror_id:      0
    lcme_flags:          extension
    lcme_extent.e_start: 6979321856
    lcme_extent.e_end:   EOF
      lmm_stripe_count:  0
      lmm_extension_size: 268435456
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: -1


________________________________
From: lustre-discuss <[email protected]> on behalf of 
BALVERS Martin via lustre-discuss <[email protected]>
Sent: Tuesday, July 29, 2025 09:19
To: Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] 
<[email protected]>; lustre-discuss <[email protected]>
Subject: Re: [lustre-discuss] [EXTERNAL] [BULK] No ZFS compression on OST's 
when using PFL

WARNING - EXTERNAL SENDER - BE CYBERSAFE

Hi,

My initial copy from old lustre to new lustre was with rsync, using this syntax:
SOURCE="/lustre/workgroups" DEST="${SOURCE#/lustre/}" && find "$SOURCE" 
-maxdepth 1 -mindepth 1 -type d | xargs -t -n1 -P6 -I% rsync -aPA 
--delete-during % "/mnt/lustre_new/$DEST"

I do indeed need to copy the linux ACL's

But when debugging the issue, I used files without any extended attributes, 
from other filesystems than lustre.
Just enabling DoM with "lfs setstripe -E 1M -L mdt -E -1 -c 1 
/mnt/lustre_new/dom" will disable compression on the OST's. (dom_stripesize is 
set to 1048576)

I'm thinking about trying 2.15.1 on the new servers...

Regards,
Martin Balvers


________________________________
From: Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.] 
<[email protected]>
Sent: Monday, July 28, 2025 16:57
To: BALVERS Martin <[email protected]>; lustre-discuss 
<[email protected]>
Subject: Re: [EXTERNAL] [BULK] [lustre-discuss] No ZFS compression on OST's 
when using PFL

WARNING - EXTERNAL SENDER - BE CYBERSAFE


I’m not sure if this is related to your problem but you need to be careful when 
copying data between two lustre filesystems.  If you use something that copies 
the extended attributes (e.g. rsync -X), you can copy the lustre xattrs, which 
is probably not what you want.  This will override the PFL you have on the new 
lustre FS.  You can either not copy the extended attributes (which isn’t a 
great option if you are using ACL’s or other xattrs) or use a lustre-aware tool 
like mpifileutils.



From: lustre-discuss <[email protected]> on behalf of 
BALVERS Martin via lustre-discuss <[email protected]>
Date: Friday, July 25, 2025 at 7:07 AM
To: lustre-discuss <[email protected]>
Subject: [EXTERNAL] [BULK] [lustre-discuss] No ZFS compression on OST's when 
using PFL

CAUTION: This email originated from outside of NASA.  Please take care when 
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Hi,



I am using a lustre 2.15.1 cluster with PFL. I'm using the following layout:

lfs setstripe -E 1M -L mdt -E 128M -c 1 -S 4M -E 2G -c 2 -z 64M -E -1 -c -1 -z 
256M /lustre



OST's have zpools with zstd compression enabled.

This has worked fine for me for many years.



I now have new servers and installed 2.16.1 on them. I used the same PFL 
layout, and after some benchmarking I proceeded to copy data from the old 
lustre to the new.

After a while I noticed that it was filling up faster that expected, and say 
that the compression ratio on the zpools was 1.



Compression on the zpools is enabled, it should have worked as far as I can 
tell.

When I disable PFL, compression works as expected.



I have attached the some results in a txt file.



I have also tried 2.15.7 with the same results. Enabling PFL, or just DoM 
disables compression on the OST's.



Am I missing something obvious here?



Regards,

Martin Balvers

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