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> From: Jan-Frode Myklebust
> To: gpfsug main d
rgericht: Amtsgericht Stuttgart, HRB 17122
From: "Uwe Falke"
To: gpfsug main discussion list
Date: 28/05/2021 22:04
Subject: [EXTERNAL] Re: [gpfsug-discuss] Long IO waiters and IBM
Storwize V5030
Sent by:gpfsug-discuss-boun...@spectrumscale.org
Hi, odd prefetch str
Ehningen
Registergericht: Amtsgericht Stuttgart, HRB 17122
From: Jan-Frode Myklebust
To: gpfsug main discussion list
Date: 28/05/2021 19:50
Subject:[EXTERNAL] Re: [gpfsug-discuss] Long IO waiters and IBM
Storwize V5030
Sent by:gpfsug-discuss-boun...@spectrumscale.org
One thing
Hi Folks,
So, we are experiencing some very long IO waiters in our GPFS cluster:
# mmdiag --waiters
=== mmdiag: waiters ===
Waiting 17.3823 sec since 10:41:01, monitored, thread 21761 NSDThread: for I/O
completion
Waiting 16.6140 sec since 10:41:02, monitored, thread 21730 NSDThread: for
One thing to check: Storwize/SVC code will *always* guess wrong on
prefetching for GPFS. You can see this with having a lot higher read data
throughput on mdisk vs. on on vdisks in the webui. To fix it, disable
cache_prefetch with "chsystem -cache_prefetch off".
This being a global setting, you
