Parallel rsync

Following steps did the job for me:

1. Run the rsync --dry-run first in order to get the list of files those would be affected.

rsync -avzm --stats --safe-links --ignore-existing --dry-run --human-readable /data/projects REMOTE-HOST:/data/ > /tmp/transfer.log

2. I fed the output of cat transfer.log to parallel in order to run 5 rsyncs in parallel, as follows:

cat /tmp/transfer.log | parallel --will-cite -j 5 rsync -avzm --relative --stats --safe-links --ignore-existing --human-readable {} REMOTE-HOST:/data/ > result.log

Here, --relative option (link) ensured that the directory structure for the affected files, at the source and destination, remains the same (inside /data/ directory), so the command must be run in the source folder (in example, /data/projects).