Thanks Julien for the answer.
You are right.
I had tested others solutions and i found that the black screen comes from the boot config in linux.
During Installation, the default option for "boot loader" was on the /dev/sdb (shared HD) (???) so i changed it to /dev/sda (1st HD). Apparently, that was the mistake.
So i deleted my VM and started again without the shared disk.
I installed RHEL on 1st HD after partitionning it, success after reboot.
Then, i add the shared HD to the VM.
The VM perfectly reboots.