Boot issue when cloning disk with clonezilla until I switch to sata

[pep]

Hi there,
I face a strange issue.
I have a linux VM 250GB with scsi0 virtio device. I reduced the partition size to 80GB thanks to gparted and was still able to boot it (disk was still 250GB in size but OS see a partition of 80GB.
Next I clone the VM with clonezilla onto a 80GB scsi1 disk.
Once cloned I removed the scsi0 and try to boot on scsi1 without success.
I tried everything possible :
- dd if=/dev/sda of=/dev/sdb bs=2048 count=1
- install grub on sdb (80GB) and try to boot.

What works:
- keep /dev/sda (250GB) and boot from there to /dev/sdb1 with grub from sda ...
- OR switch 80GB disk to "sata0" and remove the other one, in this case the BIOS is able to boot...

Is this normal?
Is there a way to be able to boot from scsi0 (virtio) as with the 250GB disk? In theory there should not be any difference :/...

Thanks for any ideas!

 

[pep]

Even more stange...
Since I boot a first with sata0 and shutdown, I can now boot as scsi0 ...
:/
If you what was the issue, I'll be very thankful!