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 ------------------------------------------------------------------------------------------------------------------ If you feel that your question can benefit other users of Spectrum Scale (GPFS), then please post it to the public IBM developerWroks Forum at https://www.ibm.com/developerworks/community/forums/html/forum?id=11111111-0000-0000-0000-000000000479 . If your query concerns a potential software error in Spectrum Scale (GPFS) and you have an IBM software maintenance contract please contact 1-800-237-5511 in the United States or your local IBM Service Center in other countries. The forum is informally monitored as time permits and should not be used for priority messages to the Spectrum Scale (GPFS) team. From: "Oesterlin, Robert" <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 06/12/2017 04:43 PM Subject: Re: [gpfsug-discuss] Meaning of API Stats Category Sent by: [email protected] 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: <[email protected]> on behalf of Kristy Kallback-Rose <[email protected]> Reply-To: gpfsug main discussion list <[email protected]> Date: Monday, June 12, 2017 at 3:17 PM To: gpfsug main discussion list <[email protected]> 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"? _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss
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