Yes large or huge database is problem for live backup. If you have performance problems with your server while making hot / live backups, try any one of the solution
#1. Set up replication and perform backups on the slave rather than on the master ... see this tutorial
ONLamp.com -- Live Backups of MySQL Using Replication
#2. Use a Veritas filesystem to make snapshots (you need Veritas product

__________________
Rocky Jr.
You may have my body & soul, but you will never touch my pride!
If you have knowledge, let others light their candles at it.
Certified to work on
HP-UX /
Sun Solaris /
RedHat