=== About block.db sizing ===
As usual, there’s something wrong :Who's tired of spillovers? Everyone's tired of spillovers! Spillover is when you use Bluestore in an SSD+HDD configuration putting Bluestore’s database (block.db)on the SSD partition, but it constantly spills over to the HDD. This often happens despite that SSD partition is much larger than the actual DB. Spillovers show up with a warning in `ceph -s` starting with Ceph 14 Nautilus. There’s also an attempt to fix them with additional RocksDB «allocation hints» in Ceph 15 Octopus, however, generally the situation is still the same as before.
Official documents say that you should allocate 4 % of the slow device space for block.db (Bluestore’s metadata partition). This is a lot, Bluestore rarely needs that amount of space.
