Re: [gpfsug-discuss] Client Latency and High NSD Server Load Average

Frederick Stock Thu, 04 Jun 2020 04:09:37 -0700

From the waiters you provided I would guess there is something amiss with some of your storage systems. Since those waiters are on NSD servers they are waiting for IO requests to the kernel to complete. Generally IOs are expected to complete in milliseconds, not seconds. You could look at the output of "mmfsadm dump nsd" to see how the GPFS IO queues are working but that would be secondary to checking your storage systems.

Fred
__________________________________________________
Fred Stock | IBM Pittsburgh Lab | 720-430-8821
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----- Original message -----
From: "Saula, Oluwasijibomi" <[email protected]>
Sent by: [email protected]
To: "[email protected]" <[email protected]>
Cc:
Subject: [EXTERNAL] Re: [gpfsug-discuss] Client Latency and High NSD Server Load Average
Date: Wed, Jun 3, 2020 6:24 PM

Frederick,

Yes on both counts! - mmdf is showing pretty uniform (ie 5 NSDs out of 30 report 65% free; All others are uniform at 58% free)...

NSD servers per disks are called in round-robin fashion as well, for example:

gpfs1 tier2_001 nsd02-ib,nsd03-ib,nsd04-ib,tsm01-ib,nsd01-ib

gpfs1 tier2_002 nsd03-ib,nsd04-ib,tsm01-ib,nsd01-ib,nsd02-ib

gpfs1 tier2_003 nsd04-ib,tsm01-ib,nsd01-ib,nsd02-ib,nsd03-ib

gpfs1 tier2_004 tsm01-ib,nsd01-ib,nsd02-ib,nsd03-ib,nsd04-ib

Any other potential culprits to investigate?

I do notice nsd03/nsd04 have long waiters, but nsd01 doesn't (nsd02-ib is offline for now):
[nsd03-ib ~]# mmdiag --waiters

=== mmdiag: waiters ===

Waiting 6.5113 sec since 17:17:33, monitored, thread 4175 NSDThread: for I/O completion

Waiting 6.3810 sec since 17:17:33, monitored, thread 4127 NSDThread: for I/O completion

Waiting 6.1959 sec since 17:17:34, monitored, thread 4144 NSDThread: for I/O completion

nsd04-ib:

Waiting 13.1386 sec since 17:19:09, monitored, thread 9971 NSDThread: for I/O completion

Waiting 10.3562 sec since 17:19:12, monitored, thread 9958 NSDThread: for I/O completion

Waiting 10.0338 sec since 17:19:12, monitored, thread 9951 NSDThread: for I/O completion

tsm01-ib:

Waiting 8.1211 sec since 17:20:24, monitored, thread 3644 NSDThread: for I/O completion

Waiting 7.6690 sec since 17:20:24, monitored, thread 3641 NSDThread: for I/O completion

Waiting 7.4969 sec since 17:20:24, monitored, thread 3658 NSDThread: for I/O completion

Waiting 7.3573 sec since 17:20:24, monitored, thread 3642 NSDThread: for I/O completion

nsd01-ib:

Waiting 0.2548 sec since 17:21:47, monitored, thread 30513 NSDThread: for I/O completion

Waiting 0.1502 sec since 17:21:47, monitored, thread 30529 NSDThread: for I/O completion

Thanks,

Oluwasijibomi (Siji) Saula

HPC Systems Administrator / Information Technology

Research 2 Building 220B / Fargo ND 58108-6050

p: 701.231.7749 / www.ndsu.edu

From: [email protected] <[email protected]> on behalf of [email protected] <[email protected]>
Sent: Wednesday, June 3, 2020 4:56 PM
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Subject: gpfsug-discuss Digest, Vol 101, Issue 6

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Today's Topics:

   1. Introducing SSUG::Digital
      (Simon Thompson (Spectrum Scale User Group Chair))
   2. Client Latency and High NSD Server Load Average
      (Saula, Oluwasijibomi)
   3. Re: Client Latency and High NSD Server Load Average
      (Frederick Stock)

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Message: 1
Date: Wed, 03 Jun 2020 20:11:17 +0100
From: "Simon Thompson (Spectrum Scale User Group Chair)"
        <[email protected]>
To: "[email protected]"
        <[email protected]>
Subject: [gpfsug-discuss] Introducing SSUG::Digital
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Hi All.,

I happy that we can finally announce SSUG:Digital, which will be a series of online session based on the types of topic we present at our in-person events.

I know it?s taken use a while to get this up and running, but we?ve been working on trying to get the format right. So save the date for the first SSUG:Digital event which will take place on Thursday 18th June 2020 at 4pm BST. That?s:
San Francisco, USA at 08:00 PDT
New York, USA at 11:00 EDT
London, United Kingdom at 16:00 BST
Frankfurt, Germany at 17:00 CEST
Pune, India at 20:30 IST
We estimate about 90 minutes for the first session, and please forgive any teething troubles as we get this going!

(I know the times don?t work for everyone in the global community!)

Each of the sessions we run over the next few months will be a different Spectrum Scale Experts or Deep Dive session.

More details at:

https://www.spectrumscaleug.org/introducing-ssugdigital/

(We?ll announce the speakers and topic of the first session in the next few days ?)

Thanks to Ulf, Kristy, Bill, Bob and Ted for their help and guidance in getting this going.

We?re keen to include some user talks and site updates later in the series, so please let me know if you might be interested in presenting in this format.

Simon Thompson

SSUG Group Chair

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Message: 2
Date: Wed, 3 Jun 2020 21:45:05 +0000
From: "Saula, Oluwasijibomi" <[email protected]>
To: "[email protected]"
        <[email protected]>
Subject: [gpfsug-discuss] Client Latency and High NSD Server Load
        Average
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        <dm6pr08mb5324b014bc4aa03ccf25557598...@dm6pr08mb5324.namprd08.prod.outlook.com>

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Hello,

Anyone faced a situation where a majority of NSDs have a high load average and a minority don't?

Also, is 10x NSD server latency for write operations than for read operations expected in any circumstance?

We are seeing client latency between 6 and 9 seconds and are wondering if some GPFS configuration or NSD server condition may be triggering this poor performance.

Thanks,

Oluwasijibomi (Siji) Saula

HPC Systems Administrator / Information Technology

Research 2 Building 220B / Fargo ND 58108-6050

p: 701.231.7749 / www.ndsu.edu<http://www.ndsu.edu/>

[cid:[email protected]]

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Message: 3
Date: Wed, 3 Jun 2020 21:56:04 +0000
From: "Frederick Stock" <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: [gpfsug-discuss] Client Latency and High NSD Server Load
        Average
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