your physical device limitations (much more noticeable on a hard disk drive than a solid-state drive… Why?).

There are bigger factors that influence performance, such as: QEMU advises against using QED.Įach of the formats may have nuanced performance characteristics due to how the block storage is abstracted by the format, but I haven't found any benchmarks comparing the VirtualBox-supported formats. QED was an abandoned enhancement of qcow2. It has been superseded by qcow2, which VirtualBox does not support. QCOW is the old original version of the qcow format. This probably isn't suitable for you, especially considering that VirtualBox only supports an old version of the HDD format. Parallels specializes in virtualization for macOS. Windows Server 2012 introduced VHDX as the successor to VHD, but VirtualBox does not support VHDX. VHD is the native format of Microsoft Virtual PC. This format might be the the best choice for you because you want wide compatibility with other virtualization software. VMDK is developed by and for VMWare, but VirtualBox and QEMU (another common virtualization software) also support it. Other virtualization software generally don't support VDI, but it's pretty easy to convert from VDI to another format, especially with qemu-img convert. be able to move my virtual machine to another OS or even another free virtualization solution with minimal effort (probably something that would run fine on Ubuntu).VirtualBox supports snapshotting of all six formats. HDD, QCOW, and QED have to be dynamically allocated if created in VirtualBox. VMDK has an additional capability of splitting the storage file into files less than 2 GB each, which is useful if your file system has a small file size limit. VDI, VMDK, and VHD all support dynamically allocated storage.

Source: Oracle® VM VirtualBox® User Manual » Chapter 5.

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