While trying to migrate a virtual machine running on Hyper-V from one cluster to another using SCVMM 2008 R2 I got an error in the Migration wizard: Not enough disk space on volumes: Maximum disk space is 1048451 MB.
Situation: this VM has large VHD files on different CSV volumes. It has a VHD on volume 1 with a size of 850 GB. It also has a VHD on volume 2 with a size of 300 GB. Both VHDs are on different adapters (IDE and SCSI). The destination cluster has two empty CSV volumes with both 1 TB available disk space.
So there is enough diskspace at the target to perform the storage migration. However, SCVMM adds sizes of all VHD files and when this is over the capacity of the largest CSV in the target the migration cannot be performed using the GUI of SCVMM 2008.