[gpfsug-discuss] Well, this is the pits...
Buterbaugh, Kevin L
Kevin.Buterbaugh at Vanderbilt.Edu
Thu May 4 17:56:26 BST 2017
Hi Kums,
Thanks for the info on the releases … can you clarify about pitWorkerThreadsPerNode? As I said in my original post, on all 8 NSD servers and the filesystem manager it is set to zero. No matter how many times I add zero to zero I don’t get a value > 31! ;-) So I take it that zero has some sort of unspecified significance? Thanks…
Kevin
On May 4, 2017, at 11:49 AM, Kumaran Rajaram <kums at us.ibm.com<mailto:kums at us.ibm.com>> wrote:
Hi,
>>I’m running 4.2.2.3 on my GPFS servers (some clients are on 4.2.1.1 or 4.2.0.3 and are gradually being upgraded). What version of GPFS fixes this? With what I’m doing I need the ability to run mmrestripefs.
GPFS version 4.2.3.0 (and above) fixes this issue and supports "sum of pitWorkerThreadsPerNode of the participating nodes (-N parameter to mmrestripefs)" to exceed 31.
If you are using 4.2.2.3, then depending on "number of nodes participating in the mmrestripefs" then the GPFS config parameter "pitWorkerThreadsPerNode" need to be adjusted such that "sum of pitWorkerThreadsPerNode of the participating nodes <= 31".
For example, if "number of nodes participating in the mmrestripefs" is 6 then adjust "mmchconfig pitWorkerThreadsPerNode=5 -N <participating_nodes>". GPFS would need to be restarted for this parameter to take effect on the participating_nodes (verify with mmfsadm dump config | grep pitWorkerThreadsPerNode)
Regards,
-Kums
From: "Buterbaugh, Kevin L" <Kevin.Buterbaugh at Vanderbilt.Edu<mailto:Kevin.Buterbaugh at Vanderbilt.Edu>>
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Date: 05/04/2017 12:08 PM
Subject: Re: [gpfsug-discuss] Well, this is the pits...
Sent by: gpfsug-discuss-bounces at spectrumscale.org<mailto:gpfsug-discuss-bounces at spectrumscale.org>
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Hi Olaf,
I didn’t touch pitWorkerThreadsPerNode … it was already zero.
I’m running 4.2.2.3 on my GPFS servers (some clients are on 4.2.1.1 or 4.2.0.3 and are gradually being upgraded). What version of GPFS fixes this? With what I’m doing I need the ability to run mmrestripefs.
It seems to me that mmrestripefs could check whether QOS is enabled … granted, it would have no way of knowing whether the values used actually are reasonable or not … but if QOS is enabled then “trust” it to not overrun the system.
PMR time? Thanks..
Kevin
On May 4, 2017, at 10:54 AM, Olaf Weiser <olaf.weiser at de.ibm.com<mailto:olaf.weiser at de.ibm.com>> wrote:
HI Kevin,
the number of NSDs is more or less nonsense .. it is just the number of nodes x PITWorker should not exceed to much the #mutex/FS block
did you adjust/tune the PitWorker ? ...
so far as I know.. that the code checks the number of NSDs is already considered as a defect and will be fixed / is already fixed ( I stepped into it here as well)
ps. QOS is the better approach to address this, but unfortunately.. not everyone is using it by default... that's why I suspect , the development decide to put in a check/limit here .. which in your case(with QOS) would'nt needed
From: "Buterbaugh, Kevin L" <Kevin.Buterbaugh at Vanderbilt.Edu<mailto:Kevin.Buterbaugh at Vanderbilt.Edu>>
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Date: 05/04/2017 05:44 PM
Subject: Re: [gpfsug-discuss] Well, this is the pits...
Sent by: gpfsug-discuss-bounces at spectrumscale.org<mailto:gpfsug-discuss-bounces at spectrumscale.org>
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Hi Olaf,
Your explanation mostly makes sense, but...
Failed with 4 nodes … failed with 2 nodes … not gonna try with 1 node. And this filesystem only has 32 disks, which I would imagine is not an especially large number compared to what some people reading this e-mail have in their filesystems.
I thought that QOS (which I’m using) was what would keep an mmrestripefs from overrunning the system … QOS has worked extremely well for us - it’s one of my favorite additions to GPFS.
Kevin
On May 4, 2017, at 10:34 AM, Olaf Weiser <olaf.weiser at de.ibm.com<mailto:olaf.weiser at de.ibm.com>> wrote:
no.. it is just in the code, because we have to avoid to run out of mutexs / block
reduce the number of nodes -N down to 4 (2nodes is even more safer) ... is the easiest way to solve it for now....
I've been told the real root cause will be fixed in one of the next ptfs .. within this year ..
this warning messages itself should appear every time.. but unfortunately someone coded, that it depends on the number of disks (NSDs).. that's why I suspect you did'nt see it before
but the fact , that we have to make sure, not to overrun the system by mmrestripe remains.. to please lower the -N number of nodes to 4 or better 2
(even though we know.. than the mmrestripe will take longer)
From: "Buterbaugh, Kevin L" <Kevin.Buterbaugh at Vanderbilt.Edu<mailto:Kevin.Buterbaugh at Vanderbilt.Edu>>
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Date: 05/04/2017 05:26 PM
Subject: [gpfsug-discuss] Well, this is the pits...
Sent by: gpfsug-discuss-bounces at spectrumscale.org<mailto:gpfsug-discuss-bounces at spectrumscale.org>
________________________________
Hi All,
Another one of those, “I can open a PMR if I need to” type questions…
We are in the process of combining two large GPFS filesystems into one new filesystem (for various reasons I won’t get into here). Therefore, I’m doing a lot of mmrestripe’s, mmdeldisk’s, and mmadddisk’s.
Yesterday I did an “mmrestripefs <old fs> -r -N <my 8 NSD servers>” (after suspending a disk, of course). Worked like it should.
Today I did a “mmrestripefs <new fs> -b -P capacity -N <those same 8 NSD servers>” and got:
mmrestripefs: The total number of PIT worker threads of all participating nodes has been exceeded to safely restripe the file system. The total number of PIT worker threads, which is the sum of pitWorkerThreadsPerNode of the participating nodes, cannot exceed 31. Reissue the command with a smaller set of participating nodes (-N option) and/or lower the pitWorkerThreadsPerNode configure setting. By default the file system manager node is counted as a participating node.
mmrestripefs: Command failed. Examine previous error messages to determine cause.
So there must be some difference in how the “-r” and “-b” options calculate the number of PIT worker threads. I did an “mmfsadm dump all | grep pitWorkerThreadsPerNode” on all 8 NSD servers and the filesystem manager node … they all say the same thing:
pitWorkerThreadsPerNode 0
Hmmm, so 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 > 31?!? I’m confused...
—
Kevin Buterbaugh - Senior System Administrator
Vanderbilt University - Advanced Computing Center for Research and Education
Kevin.Buterbaugh at vanderbilt.edu<mailto:Kevin.Buterbaugh at vanderbilt.edu>- (615)875-9633
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