[ceph-users] Re: MDS cache tunning

I've seen your other thread. Using 78GB of RAM when the memory limit is set to 64GB is not highly unusual, and doesn't necessarily indicate any problem. It *would* be a problem if the MDS memory grows uncontrollably, however. Otherwise, check those new defaults for caps recall -- they were released around 14.2.19 IIRC. -- Dan On Wed, May 26, 2021 at 12:46 PM Andres Rojas Guerrero <a.rojas(a)csic.es> wrote: > > Thanks for the answer. Yes, during these last weeks I have had memory > consumption problems in the MDS nodes that led, at least it seemed to > me, to performance problems in CephFS. I have been varying, for example: > > mds_cache_memory_limit > mds_min_caps_per_client > mds_health_cache_threshold > mds_max_caps_per_client > mds_cache_reservation > > But without much knowledge and with a trial and error procedure, i.e. > observing how CephFS behaved when changing one of the parameters. > Although I have achieved improvement the procedure does not convince me > at all and that's why I was asking if there was something more reliable ... > > > > > El 26/5/21 a las 12:15, Dan van der Ster escribió: >> Hi, >> >> The mds_cache_memory_limit should be set to something relative to the >> RAM size of the MDS -- maybe 50% is a good rule of thumb, because >> there are a few cases where the RSS can exceed this limit. Your >> experience will help guide what size you need (metadata pool IO >> activity will be really high if the MDS cache is too small) >> >> Otherwise, in recent releases of N/O/P the defaults for those settings >> you mentioned are quite good [1]; I would be surprised if they need >> further tuning for 99% of users. >> Is there any reason you want to start adjusting these params? >> >> Best Regards, >> >> Dan >> >> [1] https://github.com/ceph/ceph/pull/38574 >> >> On Wed, May 26, 2021 at 11:58 AM Andres Rojas Guerrero <a.rojas(a)csic.es> wrote: >>> >>> Hi all, I have observed that the MDS Cache Configuration has 18 parameters: >>> >>> mds_cache_memory_limit >>> mds_cache_reservation >>> mds_health_cache_threshold >>> mds_cache_trim_threshold >>> mds_cache_trim_decay_rate >>> mds_recall_max_caps >>> mds_recall_max_decay_threshold >>> mds_recall_max_decay_rate >>> mds_recall_global_max_decay_threshold >>> mds_recall_warning_threshold >>> mds_recall_warning_decay_rate >>> mds_session_cap_acquisition_throttle >>> mds_session_cap_acquisition_decay_rate >>> mds_session_max_caps_throttle_ratio >>> mds_cap_acquisition_throttle_retry_request_timeout >>> mds_session_cache_liveness_magnitude >>> mds_session_cache_liveness_decay_rate >>> mds_max_caps_per_client >>> >>> >>> >>> I find the Ceph documentation in this section a bit cryptic and I have >>> tried to find some resources that talk about how to tune these >>> parameters, but without success. >>> >>> Does anyone have experience in adjusting these parameters according to >>> the characteristics of the Ceph cluster itself, the hardware and the use >>> of MDS? >>> >>> Regards! >>> -- >>> ******************************************************* >>> Andrés Rojas Guerrero >>> Unidad Sistemas Linux >>> Area Arquitectura Tecnológica >>> Secretaría General Adjunta de Informática >>> Consejo Superior de Investigaciones Científicas (CSIC) >>> Pinar 19 >>> 28006 - Madrid >>> Tel: +34 915680059 -- Ext. 990059 >>> email: a.rojas(a)csic.es >>> ID comunicate.csic.es: @50852720l:matrix.csic.es >>> ******************************************************* >>> _______________________________________________ >>> ceph-users mailing list -- ceph-users(a)ceph.io >>> To unsubscribe send an email to ceph-users-leave(a)ceph.io > > -- > ******************************************************* > Andrés Rojas Guerrero > Unidad Sistemas Linux > Area Arquitectura Tecnológica > Secretaría General Adjunta de Informática > Consejo Superior de Investigaciones Científicas (CSIC) > Pinar 19 > 28006 - Madrid > Tel: +34 915680059 -- Ext. 990059 > email: a.rojas(a)csic.es > ID comunicate.csic.es: @50852720l:matrix.csic.es > *******************************************************