--hfsCompression
When copying files or extracting content from an archive,
if the destination is an HFS+ volume that supports compres-
sion, all the content will be compressed if appropriate.
This is only supported on Mac OS X 10.6 or later, and is
[B]only intended to be used in installation and backup scenar-
ios that involve system files[/B]. Since files using HFS+ com-
pression are not readable on versions of Mac OS X earlier
than 10.6, this flag should not be used when dealing with
non-system files or other user-generated content.