[lustre-discuss] lustre-discuss Digest, Vol 217, Issue 19 Files created in append mode don't obey

[John Bauer]

I ran strace just to determine what is called here.  bash used 
openat(,,O_WRONLY,O_CREAT|O_APPEND) to open the file and I thought 
openat() might be the issue, so I wrote a simple program to test. Turns 
out that it is the O_APPEND bit, with either open() or openat() that 
causes the behavior.

On 4/29/24 10:21, lustre-discuss-request at lists.lustre.org wrote:
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>     1. Re: [EXTERNAL] [BULK] Files created in append mode don't obey
>        directory default stripe count
>        (Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.])
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 29 Apr 2024 15:21:06 +0000
> From: "Vicker, Darby J. (JSC-EG111)[Jacobs Technology, Inc.]"
> 	<darby.vicker-1 at nasa.gov>
> To: "Otto, Frank" <f.otto at ucl.ac.uk>,
> 	"lustre-discuss at lists.lustre.org" <lustre-discuss at lists.lustre.org>
> Subject: Re: [lustre-discuss] [EXTERNAL] [BULK] Files created in
> 	append mode don't obey directory default stripe count
> Message-ID:
> 	<DM6PR09MB4662E01CBDC1827F3D92C077E91B2 at DM6PR09MB4662.namprd09.prod.outlook.com>
> 	
> Content-Type: text/plain; charset="windows-1252"
>
> 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
> CAUTION: This email originated from outside of NASA.  Please take care when clicking links or opening attachments.  Use the "Report Message" button to report suspicious messages to the NASA SOC.
>
>
> 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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