CEPH shared SSD for DB/WAL?

[abrakadabra]

I am evaluating VMware vSphere and Proxmox VE. I think the relationship between OSD and DB/WAL in ceph may be very similar to the disk group in vSAN. Once the cache disk fails, the entire disk group will not work.
There is a very confusing point in ceph. What is the relationship between Cache Tiering and DB/WAL in BlueStore. If the HCI cluster needs to be built at present, what method should be adopted to handle SSD and HDD mixed disks.

I think this is the wrong thread for this question. I just want to point out that Cache Tiering is deprecated:

Cache tiering has been deprecated in the Reef release as it has lacked a maintainer for a very long time. This does not mean it will be certainly removed, but we may choose to remove it without much further notice.