OSDに対するBlueStoreサイズ

https://access.redhat.com/documentation/ja-jp/red_hat_ceph_storage/4/html/administration_guide/sizing-considerations-for-ceph-bluestore_admin

The general recommendation is to have block.db size in between 1% to 4% of block size. For RGW workloads, it is 
recommended that the block.db size isn’t smaller than 4% of block, because RGW heavily uses it to store its 
metadata. For example, if the block size is 1TB, then block.db shouldn’t be less than 40GB. For RBD workloads, 1% 
to 2% of block size is usually enough.

rocksdb = 2%
waldb = 0.02%

下記も参考RAM/CPUサイジング
16 Ceph サイジング(RAM/CPU)