@olivierlambert said in Same CPU XEON 4309Y but migration failed because some CPU features missing !:
It could be microcode update and BIOS update making that change. Since they are not in the same pool, this can be expected. Indeed, migrate to the more recent, upgrade the old one/reboot and that should do the trick.
Yes, the BIOS/microcode differences do sometimes change the CPU mask. They need to be identical in many cases on all hosts within a pool.