Adding Disk to Physical Exchange Servers

Greetings,

I have Exchange Server 2007 setup.

Having 2 Mailbox Server and 2 CAS Servers.

The Mailbox Server (Database drive) is running Low disk space on both the Mailbox servers.

Now i want to add Physical Disks to both the servers. I have already bought 5 HDD (300GB each).

Please let me know how to add disk space to both the Mailbox servers without any downtime.

Thanks in advance.

Best Regards

K2