[ceph-users] Benchmark WAL/DB on SSD and HDD for RGW RBD CephFS

Hi all, I'm trying to find performance penalty with OSD HDD when using WAL/DB in faster device (SSD/NVMe) vs WAL/DB in same device (HDD) for different workload (RBD, RGW with index bucket in SSD pool, and CephFS with metadata in SSD pool). I want to know if giving up disk slot for WAL/DB device is worth vs adding more OSD. Unfortunately I cannot find the benchmark for these kind workload. Has anyone ever done this benchmark? Thank you.