Make a Backup

Hi, this is the scenario: I have 2 PowerEdge 1950, one of them with two disk of 300 GB with a Raid1 array, this server is in operation. The other server has two disks of 147 GB, and this one is not in use. I want to make a backup of the data of the first Power Edge over the second, and then uncofig the Raid1 of the first server and remake a Raid0, so I can have more space in disk in order to at last get back the backup data that was in the second server again to the first.

How I can make the backup??? Help please...

PD. I am using FreeBSD as OS in the server in operation.