rsync 3.1.1 zlib might not work

[Dewayne Geraghty]

Emanuel,
Thanks for bringing to our attention, I transmit ~900MB of backups over
the WAN  rather than the uncompressed 9G database. You've saved a client
excess use charges.

I tested using highly compressible data (mostly nulls) and it seems to
work as expected.

Without -z or -zz: Sent 593 bytes speadup 0.82
With -z :  Sent 593 bytes speadup 0.82    (Unexpected.  Should be in
ports/UPDATING)
With -zz: sent 85 bytes speedup is 4.27   (Expected)

Detail
# rm ./b && printf "%512c"a > a && rsync -av ./a ./b
sending incremental file list
a

sent 593 bytes  received 35 bytes  1,256.00 bytes/sec
total size is 512  speedup is 0.82

# rm ./b && printf "%512c"a > a && rsync -avz ./a ./b
This rsync lacks old-style --compress due to its external zlib.  Try -zz.
Continuing without compression.

sending incremental file list
a

sent 593 bytes  received 35 bytes  1,256.00 bytes/sec
total size is 512  speedup is 0.82

# rm ./b && printf "%512c"a > a && rsync -avzz ./a ./b
sending incremental file list
a

sent 85 bytes  received 35 bytes  240.00 bytes/sec
total size is 512  speedup is 4.27

# ldd `which rsync`
/usr/local/bin/rsync:
        libz.so.6 => /lib/libz.so.6 (0x800873000)
        libc.so.7 => /lib/libc.so.7 (0x800a87000)

Perhaps ports/UPDATING should alert users to the new requirement to use
-zz (not in man page) instead of -z or --compress?

Regards, Dewayne.