I use zip to do a regular backup of a local directory onto a remote machine. They don't believe in things like rsync here, so it's the best I can do (?). Here's the script I use

echo $(date)>>~/backuplog.txt;
if [[ -e /Volumes/backup/ ]];
then 
    cd /Volumes/Non-RAID_Storage/;
    for file in projects/*; 
        do nice -n 10 zip -vru9 /Volumes/backup/nonRaidStorage.backup.zip "$file" 2>&1 | grep -v "zip info: local extra (21 bytes)">>~/backuplog.txt;
    done;
else 
    echo "backup volume not mounted">>~/backuplog.txt;
fi

this all works fine, except that zip never uses much CPU, so it seems to be taking longer than it should. It never seems to get above 5%. I tried making it nice -20 but that didn't make any difference. Is it just the network or disc speeds bottlenecking the process or am I doing something wrong?