What do you do when your database is falling behind?
1. Optimize the queries that are running on your database.
2. Try to partition your data so extensive I/O database will be distributed evenly.
If both approach don't work, you have one option left and that is to migrate your database to a new hardware. Here are pointers on what you have to do.
1. Backup your previous data.
2. Make sure that the new hardware configuration is identical with the old hardware.
3. Prepare for a downtime meaning you have to shutdown your database.
4. Copy your data to the new hardware.
5. Test your data in the new hardware.