Assume that the disk space required for a boot image and the application data is 20 GB. Out of this, only 4 GB is used by the operating system and the remaining 16 GB is the space for applications to write. Any data or binaries that are required by each instance of the virtual machine can still be part of the first 4 GB of the shared extent. Since most of the writes are expected to take place on the 16 GB portion, you should allocate the master image in such a way that the 16 GB of space is not shared, as shown in the following commands:

  # touch /vdi_images/master_image
  # /opt/VRTS/bin/setext -r 4g -f chgsize /vdi_images/master_image
  # dd if=/dev/zero of=/vdi_images/master_image seek=16777215 \
  bs=1024 count=1

The last command creates a 16 GB hole at the end of the file. Since holes do not have any extents allocated, the writes to hole do not need to be unshared.