Hello all, thank you all a lot for the feedback to my question. I think that I now understand the situation better. I will talk with my coworkers and we will find a better setting for the values...
Many thanks, Philipp * Felipe Knop <[email protected]> [13.03.20 16:22]: > All, > > Looks to me that the demands of the workload will dictate how many files we > should be cache, that is: maxStatCache + maxFilesToCache . > > The "mix" between maxStatCache and maxFilesToCache depends on how much memory > can be made available. Accessing files from maxFilesToCache is more efficient, > but stat cache entries use much less space. > > With the > > ! maxFilesToCache 3000000 > maxStatCache 10000 > > combination, the stat cache is not providing any significant help, since only > 0.3% of the files that are cached can fit in the stat cache. If enough memory > is available then maxStatCache could be increased to (say) 3000000, at a cost > of 1.4GB. But maxFilesToCache = 3000000 uses up to 27GB. The next questions > are then > > 1) Can such memory become available on the node, given the pagepool size ? > > 2) Does the workload require caching that many files? > > > Felipe > > ---- > Felipe Knop [email protected] > GPFS Development and Security > IBM Systems > IBM Building 008 > 2455 South Rd, Poughkeepsie, NY 12601 > (845) 433-9314 T/L 293-9314 > > > > > ----- Original message ----- > From: "Frederick Stock" <[email protected]> > Sent by: [email protected] > To: [email protected] > Cc: [email protected] > Subject: [EXTERNAL] Re: [gpfsug-discuss] maxStatCache and maxFilesToCache: > Tip"gpfs_maxstatcache_low". > Date: Fri, Mar 13, 2020 10:01 AM > > As you have learned there is no simple formula for setting the > maxStatToCache, or for that matter the maxFilesToCache, configuration > values. Memory is certainly one consideration but another is directory > listing operations. The information kept in the stat cache is sufficient > for fulfilling directory listings. If your users are doing directory > listings regularly then a larger stat cache could be helpful. > > Fred > __________________________________________________ > Fred Stock | IBM Pittsburgh Lab | 720-430-8821 > [email protected] > > > > ----- Original message ----- > From: Philipp Grau <[email protected]> > Sent by: [email protected] > To: gpfsug main discussion list <[email protected]> > Cc: > Subject: [EXTERNAL] [gpfsug-discuss] maxStatCache and maxFilesToCache: > Tip "gpfs_maxstatcache_low". > Date: Fri, Mar 13, 2020 8:49 AM > > Hello, > > we have a two node NSD cluster based on a DDN system. Currently we > run Spectrum Scale 5.0.4.1 in an HPC environment. > > Mmhealth shows a tip stating "gpfs_maxstatcache_low". Our current > settings are: > > # mmdiag --config | grep -i cache > ! maxFilesToCache 3000000 > maxStatCache 10000 > > maxFilesToCache was tuned during installion and maxStatCache is the > according default value. > > After discussing this issue on the german spectumscale meeting, I > understand that it is difficult to give a formula on howto calulate > this values. > > But I learnt that a FilesToCache entry costs about 10 kbytes of memory > and a StatCache entry about 500 bytes. And typically maxStatCache > should (obviously) be greater than maxFilesToCache. There is a average > 100 GB memory usage on our systems (with a total of 265 GB RAM). > > So setting maxStatCache to at least 3000000 should be no problem. But > is that correct or to high/low? > > Has anyone some hints or thoughts on this topic? Help is welcome. > > Regards, > > Philipp > _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss
