Just to mention my own experience with P420i,
I had been running Ceph with OSDs on Raid0 for a couple of years with no problem.
When building a new cluster I recently I decided to experiment with HBA mode.
I can confirm that with PVE 8 the hpsa driver is used by linux automatically if the controller is in HBA mode.
It does work and performs fine.
BUT
it doesn't handle faulty disks very well at all.
I had a couple of disks with faults and instead of marking them as faulty and refusing to use them
the system simply locks up on retries and/or hangs.
No idea what the issue is, and I don't have the time or expertise to delve into it, although I did see someone else
on a different thread report a similar experience.
Good healthy disks are fine, but I decided I am not going to use this mode in anger, and invested in H220 HBA cards.
Its a shame because being able use this integrated controller would free up a PCI slot for something else, seems also a waste having it on the MB.