Error messages in rsync When I run

rsync -avz --exclude-from=exc ~/ /Volumes/Backup/home/


I get the message

sending incremental file list
./
.DS_Store
...&lt;snip&gt;... (lots of files).... 
End of list of files

sent 72,625,409 bytes  received 16,434 bytes  1,793,625.75 bytes/sec
total size is 28,049,731,319  speedup is 386.14
rsync error: some files/attrs were not transferred (see previous errors)
(code 23) at main.c(1249) [sender=3.1.2]


What should I do to avoid this error message?
It seems that the only thing that was missing from my rsync run was to copy extended attributes. I ran the command again, but this time adding the option -E (which I think is specific to Macs) and the job ran with no error reported.