First I'll translate the question.

Can you create a lv over two disks or not. It appears that a lv over two disks creates problems if one of the VIOS (virtual i/o server) is not available, and the other is.

Answer: yes, you can have a logical volume that uses storage from more than one "physical" volume. However, to understand, and hence come with a possible solution, I need to know a bit more. But I'll take a guess for now.

I am assumming that you are using AIX LVM mirroring and that the logical volume has one copy on a "virtual" disk coming from VIOa, and one virtual disk coming from VIOb. Using traditional AIX volume group charactistics this volume group will have two VGDA on one of the disks, and one VGDA on the other. If the VIOS hosting the disk with two VGDA becomes unavailable the VGDA quorum is lost and the logical volume volume goes offline. So, for this situation I would consider turning off quorum controls for the volume group.

Provide some feedback, and I'll introduce/describe the dangers of working without quorum checking.