параллельный ssh

split -b 500m big.tgz big.tgz-part-

for i in `ls *-part-*`; do (sleep 3; scp -P 22 -i /root/.ssh/id_rsa $i root@target:/backup/ &); done
#or
for i in `ls *-part-*`; do (sleep 3; rsync -a --rsh "ssh -p 22 -i /root/.ssh/id_rsa" $i root@target:/backup/ &); done