[ceph-users] Does it impact write performance when SSD applies into block.wal (not block.db)

Hi everyone, I saw the bluestore can separate block.db, block.wal. In my case, I'd like to apply hybrid device which uses SSD, HDD to improve the small data write performance. but I don't have enough SSD to cover block.db and block.wal. so I think it can impact performance even though SSD applies into just block.wal. I just know that block.wal depends on rocksdb cache size as parameters. SSD might not need too much. 1. When I use SSD just into block.wal, Does it impact the write performance of the small data? 2. Should I make lv of ssd per osd for block.wal? 3. How much SSD do I need for block.wal relative to HDD(if I have 100TB)?