[gpfsug-discuss] Slow performance on writes when using direct io

Grunenberg, Renar Renar.Grunenberg at huk-coburg.de
Mon Mar 11 17:04:57 GMT 2024 

Hallo Peter,
it’s difficult to give here the right recommendation, what here relevant are the io-size, the current IO-pattern of your IO’s the current config of your deamons and so on. Best is open a performance Ticket and work on this.
There are a presentation on the usergroup to hopefully figured out a little bit to these mentioned parameter. You can find this here:
https://www.spectrumscaleug.org/wp-content/uploads/2020/09/004-spectrum-scale-performance-update.pdf




Renar Grunenberg
Abteilung Informatik - Betrieb

HUK-COBURG
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96444 Coburg
Telefon:        09561 96-44110
Telefax:        09561 96-44104
E-Mail: Renar.Grunenberg at huk-coburg.de
Internet:       www.huk.de
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Von: gpfsug-discuss <gpfsug-discuss-bounces at gpfsug.org> Im Auftrag von Peter Hruška
Gesendet: Montag, 11. März 2024 16:14
An: gpfsug-discuss at gpfsug.org
Betreff: Re: [gpfsug-discuss] Slow performance on writes when using direct io

Hello Renar,

Thank you for the suggestion. I tried the configuration changes. They however do not seem to have any effect - the performance seems identical. I also tried all 4 combinations. I checked the documentation on the parameter "dioSmallSeqWriteBatching" and it states that small IOs are considered under 64kb. I've also found a parameter "dioSmallSeqWriteThreshold" but my GPFS version (5.1.9.0) claims that it's an unknown attribute.


--
S přáním pěkného dne / Best regards

Mgr. Peter Hruška
IT specialista
M Computers s.r.o.
Úlehlova 3100/10, 628 00 Brno-Líšeň (mapa<https://mapy.cz/s/gafufehufe>)
T:+420 515 538 136
E: peter.hruska at mcomputers.cz<mailto:peter.hruska at mcomputers.cz>

www.mcomputers.cz<http://www.mcomputers.cz/>
www.lenovoshop.cz<http://www.lenovoshop.cz/>
[cid:image001.png at 01DA73DD.B7502320]



On Mon, 2024-03-11 at 13:56 +0000, Grunenberg, Renar wrote:
EXTERNÍ ODESÍLATEL
Hallo Peter,
my to cents to this.
Set the diasbleDIO=yes Parameter to DEFAULT and use the

! dioSmallSeqWriteBatching 1
  disableDIO 0
And give it a try.

Regards Renar


Renar Grunenberg
Abteilung Informatik - Betrieb

HUK-COBURG
Bahnhofsplatz
96444 Coburg
Telefon:

09561 96-44110

Telefax:

09561 96-44104

E-Mail:

Renar.Grunenberg at huk-coburg.de<mailto:Renar.Grunenberg at huk-coburg.de>

Internet:

www.huk.de<http://www.huk.de>

________________________________
HUK-COBURG Haftpflicht-Unterstützungs-Kasse kraftfahrender Beamter Deutschlands a. G. in Coburg
Reg.-Gericht Coburg HRB 100; St.-Nr. 9212/101/00021
Sitz der Gesellschaft: Bahnhofsplatz, 96444 Coburg
Vorsitzender des Aufsichtsrats: Prof. Dr. Heinrich R. Schradin.
Vorstand: Klaus-Jürgen Heitmann (Sprecher), Stefan Gronbach, Dr. Hans Olav Herøy, Dr. Helen Reck, Dr. Jörg Rheinländer, Thomas Sehn, Daniel Thomas.
________________________________
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Von: gpfsug-discuss <gpfsug-discuss-bounces at gpfsug.org<mailto:gpfsug-discuss-bounces at gpfsug.org>>Im Auftrag von Peter Hruška
Gesendet: Montag, 11. März 2024 14:22
An: gpfsug-discuss at gpfsug.org<mailto:gpfsug-discuss at gpfsug.org>
Betreff: [gpfsug-discuss] Slow performance on writes when using direct io

Hello,

We encountered a problem with performance of writes on GPFS when the application uses direct io access. To simulate the issue it is enough to run fio with option direct=1. The performance drop is quite dramatic - 250 MiB/s vs. 2955 MiB/s. We've tried to instruct GPFS to ignore direct IO by using "disableDIO=yes". The directive didn't have any effect. Is there any possibility how to achieve that GPFS would ignore direct IO requests and use caching for everything?


--
S přáním pěkného dne / Best regards

Mgr. Peter Hruška
IT specialista
M Computers s.r.o.
Úlehlova 3100/10, 628 00 Brno-Líšeň (mapa<https://mapy.cz/s/gafufehufe>)
T:+420 515 538 136
E: peter.hruska at mcomputers.cz<mailto:peter.hruska at mcomputers.cz>

www.mcomputers.cz<http://www.mcomputers.cz/>
www.lenovoshop.cz<http://www.lenovoshop.cz/>
[cid:image001.png at 01DA73DD.B7502320]


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