[lustre-discuss] [EXTERNAL] [BULK] Files created in append mode don't obey directory default stripe count

[Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.]]

Wow, I would say that is definitely not expected.  I can recreate this on both of our LFS’s.  One is community lustre 2.14, the other is a DDN Exascalar.  Shown below is our community lustre but we also have a 3-segment PFL on our Exascalar and the behavor is the same there.

$ echo > aaa
$ echo >> bbb
$ lfs getstripe aaa bbb
aaa
  lcm_layout_gen:    3
  lcm_mirror_count:  1
  lcm_entry_count:   3
    lcme_id:             1
    lcme_mirror_id:      0
    lcme_flags:          init
    lcme_extent.e_start: 0
    lcme_extent.e_end:   33554432
      lmm_stripe_count:  1
      lmm_stripe_size:   4194304
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: 6
      lmm_objects:
      - 0: { l_ost_idx: 6, l_fid: [0x100060000:0xace8112:0x0] }

    lcme_id:             2
    lcme_mirror_id:      0
    lcme_flags:          0
    lcme_extent.e_start: 33554432
    lcme_extent.e_end:   10737418240
      lmm_stripe_count:  4
      lmm_stripe_size:   4194304
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: -1

    lcme_id:             3
    lcme_mirror_id:      0
    lcme_flags:          0
    lcme_extent.e_start: 10737418240
    lcme_extent.e_end:   EOF
      lmm_stripe_count:  8
      lmm_stripe_size:   4194304
      lmm_pattern:       raid0
      lmm_layout_gen:    0
      lmm_stripe_offset: -1

bbb
lmm_stripe_count:  1
lmm_stripe_size:   2097152
lmm_pattern:       raid0
lmm_layout_gen:    0
lmm_stripe_offset: 3
                obdidx                  objid                    objid                    group
                     3             179773949       0xab721fd                   0


From: lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on behalf of Otto, Frank via lustre-discuss <lustre-discuss at lists.lustre.org>
Date: Monday, April 29, 2024 at 8:33 AM
To: lustre-discuss at lists.lustre.org <lustre-discuss at lists.lustre.org>
Subject: [EXTERNAL] [BULK] [lustre-discuss] Files created in append mode don't obey directory default stripe count
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See subject. Is it a known issue? Is it expected? Easy to reproduce:


# lfs getstripe .
.
stripe_count:  4 stripe_size:   1048576 pattern:       raid0 stripe_offset: -1

# echo > aaa
# echo >> bbb
# lfs getstripe .
.
stripe_count:  4 stripe_size:   1048576 pattern:       raid0 stripe_offset: -1

./aaa
lmm_stripe_count:  4
lmm_stripe_size:   1048576
lmm_pattern:       raid0
lmm_layout_gen:    0
lmm_stripe_offset: 0
        obdidx           objid           objid           group
             0            2830          0xb0e                0
             1            2894          0xb4e                0
             2            2831          0xb0f                0
             3            2895          0xb4f                0

./bbb
lmm_stripe_count:  1
lmm_stripe_size:   1048576
lmm_pattern:       raid0
lmm_layout_gen:    0
lmm_stripe_offset: 4
        obdidx           objid           objid           group
             4            2831          0xb0f                0



As you see, file "bbb" is created with stripe count 1 instead of 4.
Observed in Lustre 2.12.x and Lustre 2.15.4.

Thanks,
Frank

--
Dr. Frank Otto
Senior Research Infrastructure Developer
UCL Centre for Advanced Research Computing
Tel: 020 7679 1506
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