Faster file transfer

We support faster file transfer or file copy, including:

• Remote file copy—Use request vmhost remote-file-copy command to copy a file directly between the hypervisor and an external fileserver.
• Local file copy of a file on the hypervisor—Use request vmhost local-file-copy command to copy a file or a directory present under /var/public/  directory structure on the hypervisor to a different name under /var/public/ directory structure