[gpfsug-discuss] Meaning of API Stats Category

[Kristy Kallback-Rose]

Thank you Eric. That did help.

On Mon, Jun 12, 2017 at 2:01 PM, IBM Spectrum Scale <scale at us.ibm.com>
wrote:

> Hello Kristy,
>
> The GPFSFileSystemAPI and GPFSNodeAPI sensor metrics are from the point of
> view of "applications" in the sense that they provide stats about I/O
> requests made to files in GPFS file systems from user level applications
> using POSIX interfaces like open(), close(), read(), write(), etc.
>
> This is in contrast to similarly named sensors without the "API" suffix,
> like GPFSFilesystem and GPFSNode.  Those sensors provide stats about I/O
> requests made by the GPFS code to NSDs (disks) making up GPFS file systems.
>
> The relationship between application I/O and disk I/O might or might not
> be obvious.  Consider some examples.  An application that starts
> sequentially reading a file might, at least initially, cause more disk I/O
> than expected because GPFS has decided to prefetch data.  An application
> write() might not immediately cause a the writing of disk blocks due to the
> operation of the pagepool.  Ultimately, application write()s might cause
> twice as much data written to disk due to the replication factor of the
> file system.  Application I/O concerns itself with user data; disk I/O
> might have to occur to handle the user data and associated file system
> metadata (like inodes and indirect blocks).
>
> The difference between GPFSFileSystemAPI and GPFSNodeAPI:
> GPFSFileSystemAPI reports stats for application I/O per filesystem per
> node; GPFSNodeAPI reports application I/O stats per node.  Similarly,
> GPFSFilesystem reports stats for disk I/O per filesystem per node; GPFSNode
> reports disk I/O stats per node.
>
> I hope this helps.
> Eric Agar
>
>
> Regards, The Spectrum Scale (GPFS) team
>
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>
> From:        "Oesterlin, Robert" <Robert.Oesterlin at nuance.com>
> To:        gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
> Date:        06/12/2017 04:43 PM
> Subject:        Re: [gpfsug-discuss] Meaning of API Stats Category
> Sent by:        gpfsug-discuss-bounces at spectrumscale.org
> ------------------------------
>
>
>
> Hi Kristy
>
> What I *think* the difference is:
>
> gpfs_fis: - calls to the GPFS file system interface
> gpfs_fs: calls from the node that actually make it to the NSD
> server/metadata
>
> The difference being what’s served out of the local node pagepool.
>
> Bob Oesterlin
> Sr Principal Storage Engineer, Nuance
>
>
> *From: *<gpfsug-discuss-bounces at spectrumscale.org> on behalf of Kristy
> Kallback-Rose <kkr at lbl.gov>
> * Reply-To: *gpfsug main discussion list <gpfsug-discuss at spectrumscale.org
> >
> * Date: *Monday, June 12, 2017 at 3:17 PM
> * To: *gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
> * Subject: *[EXTERNAL] [gpfsug-discuss] Meaning of API Stats Category
>
> Hi,
>
>   Can anyone provide more detail about what is meant by the following two
> categories of stats? The PDG has a limited description as far as I could
> see. I'm not sure what is meant by Application PoV. Would the Grafana
> bridge count as an "application"?
>
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