The keyword to search for is "deferred writes", there are several parameters that control the size and maximum number of ops that'll be "cached". Increasing to 1 MB is probably a bad idea. Paul -- Paul Emmerich Looking for help with your Ceph cluster? Contact us at https://croit.io croit GmbH Freseniusstr. 31h 81247 München www.croit.io Tel: +49 89 1896585 90 On Sat, Apr 4, 2020 at 9:41 PM <jesper@xxxxxxxx> wrote: > > > On Sat, Apr 4, 2020 at 4:13 PM <jesper@xxxxxxxx> wrote: > >> Offloading the block.db on NVMe / SSD: > >> https://docs.ceph.com/docs/mimic/rados/configuration/bluestore-config-ref/ > >> > >> Pro: Easy to deal with - seem heavily supported. > >> Con: As far as I can tell - this will only benefit the metadata of the > >> osd- not actual data. Thus a data-commit to the osd til still be > >> dominated > >> by the writelatency of the underlying - very slow HDD. > > > > small writes (<= 32kb, configurable) are written to db first and > > written back to the slow disk asynchronous to the original request. > > Now, that sounds really interesting - I havent been able to find that in > the documentation - can you provide a pointer? Whats the configuratoin > parameter named? > > Meaning moving block.dk to a say 256GB NVMe will do "the right thing" for > the system and deliver a fast write cache for smallish writes. > > Would setting the parameter til 1MB be "insane"? > > Jesper > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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