CEPH Bluestore WAL/DB on Software RAID1 for redundancy
As you may already know CEPH is not recommended to be installed over hardware/software RAID due to performance issues. but in this scenario and I will quote CEPH documentation : If there is a mix of fast and slow devices (spinning and solid state), it is recommended to place block.db on the faster device while block (data) lives on the slower (spinning drive). https://docs.ceph.com/en/octopus/rados/configuration/bluestore-config-ref/ The block.db/wal if added on faster device (ssd/nvme) and that fast device dies out you will lose all OSDs using that ssd. And based on your used CRUSH rule such event might lose all your data. so the best solution to mitigate such event is to use RAID1 for that fast device holding your block.db/wal data. If you have hardware RAID then it should be an easy task but if you don't have hardware RAID then I used this on one of my implementations:/ # Assuming we have 1TB HDD OSD pvcreate /dev/sdc # change 01 to 02 for your second OSD v