Sometimes it is necessary to download vm vdi from xenserver via http with browser.

https://:@/export_raw_vdi?vdi=&format=vhd

xe sr-list

uuid ( RO)                : 3d7a9760-cc51-4c92-b790-305aa371bf85
          name-label ( RW): Local storage
    name-description ( RW):
                host ( RO): xenxx
                type ( RO): lvm
        content-type ( RO): user

xe vdi-list sr-uuid=3d7a9760-cc51-4c92-b790-305aa371bf85

uuid ( RO)                : 2b4847e5-7b0a-45bc-ac64-f6584afb51c0
          name-label ( RW): celsius_0
    name-description ( RW): Created by XenCenter Disk Image Import
             sr-uuid ( RO): 3d7a9760-cc51-4c92-b790-305aa371bf85
        virtual-size ( RO): 236223201280
            sharable ( RO): false
           read-only ( RO): false

https:///export_raw_vdi?vdi=2b4847e5-7b0a-45bc-ac64-f6584afb51c0&format=vhd