Hi, Peter, in theory, the first node opening a file should remain metanode until it closes the file, regardless how many other nodes open it in between (if all the nodes are within the same cluster). MFT is controlling the caching inodes and - AFAIK - also of indirect blocks. A 200 GiB file will most likely have indirect blocks, but just a few up to some tens, depending on the block size in the file system. The default MFT number is much larger.
However, if you say the metanode is changing, that might cause some delays, as all token information has to be passed on to the next metanode (not sure how efficient that election is running). Having said that it could help if you use a dedicated node having the file open from start and all the time - this should prevent new metanodes being elected. If you do not get told a solution, you might want to run a trace of the mmbackup scan (maybe once with jobs accessing the file, once without). Mit freundlichen Grüßen / Kind regards Dr. Uwe Falke IT Specialist High Performance Computing Services / Integrated Technology Services / Data Center Services ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Rathausstr. 7 09111 Chemnitz Phone: +49 371 6978 2165 Mobile: +49 175 575 2877 E-Mail: uwefa...@de.ibm.com ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Business & Technology Services GmbH / Geschäftsführung: Thomas Wolter, Sven Schooß Sitz der Gesellschaft: Ehningen / Registergericht: Amtsgericht Stuttgart, HRB 17122 From: Peter Childs <p.chi...@qmul.ac.uk> To: "gpfsug-discuss@spectrumscale.org" <gpfsug-discuss@spectrumscale.org> Date: 10/07/2018 16:51 Subject: [gpfsug-discuss] Same file opened by many nodes / processes Sent by: gpfsug-discuss-boun...@spectrumscale.org We have an situation where the same file is being read by around 5000 "jobs" this is an array job in uge with a tc set, so the file in question is being opened by about 100 processes/jobs at the same time. Its a ~200GB file so copying the file locally first is not an easy answer, and these jobs are causing issues with mmbackup scanning the file system, in that the scan is taking 3 hours instead of the normal 40-60 minutes. This is read only access to the file, I don't know the specifics about the job. It looks like the metanode is moving around a fair amount (given what I can see from mmfsadm saferdump file) I'm wondering if we there is anything we can do to improve things or that can be tuned within GPFS, I'm don't think we have an issue with token management, but would increasing maxFileToCache on our token manager node help say? Is there anything else I should look at, to try and attempt to allow GPFS to share this file better. Thanks in advance Peter Childs -- Peter Childs ITS Research Storage Queen Mary, University of London _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss