Thank you for your fast answers!
I need your advice - as I know PVE officially does not support mdadm raid for their installation.
If you want RAID - PVE installer offer to use ZFS (for mirror, for example).
I have read a lot about ZFS (forums and so on) and I've got the opinion that ZFS
1) works fine at enterprise level disks only
2) takes a lot of time to learn and set up
I develop my project only with my own money, and the budget is very limited.
So I have bought a simple consumer NVMe disk, almost the cheapest (looking for a big TBW value).
When I installed PVE on this single NVMe disk it worked well and fast.
To increase reliability, I bought a second similar NVMe consumer disk of the same capacity, but from a different manufacturer (so that the disks do not fail at the same time - I have read this hint at one forum).
It is very tempting to put the system on ZFS, cause it is supported by default and "out of the box".
But I am not sure that my NMVe disks are suitable for ZFS, I afraid that the system will slow.
What do you think is the best way to proceed in my case - create RAID1 by mdadm or use ZFS for it?