qemu-imgis a Linux tool to manage QCOW2 images. TrilioVault uses a modified
qemu-imgto generate QCOW2 images. The full backup of QCOW2 image is the base image. Subsequent backups are incrementals and are overlay files each points to its previous backup.
qemu-img convertcommand traverses the backup chain and "hydrates" the entire volume contents to PV. It does not require any staging area. The data goes directly from backup media to PV.