I migrated >120 VMware virtual machines (Linux and Windows) from VMware ESXi to OpenStack. In a lab environment I also migrated from Hyper-V with these steps. Unfortunately I am not allowed to publish the script files I used for this migration, but I can publish the steps and commands that I used to migrate the virtual machines. With the steps and commands, it should be easy to create scripts that do the migration automatically.
Just to make it clear, these steps do not convert traditional (non-cloud) applications to cloud ready applications. In this case we started to use OpenStack as a traditional hypervisor infrastructure.
Update 9 September 2015: The newer versions of libguestfs-tools and qemu-img convert handle VMDK files very well (I had some issues with older versions of the tools), so the migration can be more efficient. I removed the conversion steps from VMDK to VMDK (single file) and from VMDK to RAW. The migration speed will be doubled by reducing these steps.
Disclaimer: This information is provided as-is. I will decline any responsibility caused by or with these steps and/or commands. I suggest you don’t try and/or test these commands in a production environment. Some commands are very powerful and can destroy configurations and data in Ceph and OpenStack. So always use this information with care and great responsibility.