Never migrate disks if your volume is in degraded mode. Make sure the volume is redundant first. Then follow the steps below:
Please Note: You cannot migrate disks between different CPU architectures. Sparc-based (Duo, NV+, 1100), x86-based units (NVX, Pro, 2100, 3200), and ARM-based (Duo v2, NV+ v2) cannot mix disks. Migration is only available between units with the same CPU architecture.