One tricky thing is each layer of RocksDB is 100% on SSD or 100% on HDD, so either you need to tweak the rocksdb configuration , or there will be a huge waste, e.g 20GB DB partition makes no difference compared to a 3GB one (under default rocksdb configuration)
Janne Johansson <icepic...@gmail.com> 于2020年1月14日周二 下午4:43写道： > (sorry for empty mail just before) > > >> i'm plannung to split the block db to a seperate flash device which i >>> also would like to use as an OSD for erasure coding metadata for rbd >>> devices. >>> >>> If i want to use 14x 14TB HDDs per Node >>> >>> https://docs.ceph.com/docs/master/rados/configuration/bluestore-config-ref/#sizing >>> >>> recommends a minimum size of 140GB per 14TB HDD. >>> >>> Is there any recommandation of how many osds a single flash device can >>> serve? The optane ones can do 2000MB/s write + 500.000 iop/s. >>> >> >> > I think many ceph admins are more concerned with having many drives > co-using the same DB drive, since if the DB drive fails, it also means all > OSDs are lost at the same time. > Optanes and decent NVMEs are probably capable of handling tons of HDDs, so > that the bottleneck ends up being somewhere else, but the failure scenarios > are a bit scary if the whole host is lost just by that one DB device acting > up. > > -- > May the most significant bit of your life be positive. > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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