Feature request: support skipping holes & preserve sparseness when copying sparse files

[adrien1018]

Currently when copying sparse files, rsync currently reads over all holes and transfers all zero bytes. This is extremely inefficient when transferring large sparse files (e.g. raw VM images), and the sparseness of the original file cannot be preserved (because it does not distinguish an all-zero chunk from a hole).

I'd like to suggest adding an option for (1) skipping reading / transferring holes and (2) preserve sparseness of the original file whenever possible, just like the -S option of tar.

[andreygursky]

For reference:

• Debian: #337827: rsync should handle new sparse files better with -S (06.11.2005)
• rsync@samba: #5801: Speed up delta-transfer of zeros in new files with --sparse (29.09.2008)

[drws]

This is a related feature request from the old bugtracker (just FYI).