Moving boot disk to new disks

I installed PVE on a disk, its 120GB. I want to move the boot disk to (2) SSDs in a ZFS mirror that are 500GB. I'm wondering if this will work.

Boot to live CD
dd old boot disk to new boot disk
Boot on new boot disk
Add additional boot disk as mirror

Will this work? Then, will the rest of the unused 380GB be available to be added as a new pool?