dd if=/dev/zero of=/mnt/swap16G bs=1G count=16
fallocate -l 16G mnt/swap16G
mkswap /mnt/swap16G chmod 600 /mnt/swap16G swapon /mnt/swap16G
add to the /etc/fstab if you want to keep the settings
/mnt/swapfile16g none swap sw 0 0
If using things like AWS instance-store-volume adding the file to the /etc/fstab is not appropriate.
You could create the swapfile on the fly or you could create one swapfile, compress it, and decompress on each boot.
In Ubuntu and other probably others using the /etc/rc.local file can be a decent choice (there are others).
gunzip -c /swapfile16g.gz > /mnt/swapfile16g chmod 600 /mnt/swapfile16g swapon /mnt/swapfile16G