Raid1 with 3 drives, 1 main with OS and 1 for file server (1 backup)

[Bauer17]

I am trying to do a new server install with Ubuntu server 9.10

I have 1 500MB drive that I was going to install the server software to.
Then (2) 1.5TB drives that I was going to use as a Home file server 1 with the data and 1 as a back up using raid1.

I am in the partition disk part of the install and have the following set up:

RAID1 device #0 - 1.5 TB - Software RAID device
#1 1.5TB F ext3 / (not sure if I should change this to /home)

SCSI1 (0,1,0) (sda) - 1.5TB ATA
#1 primary 1.5TB K raid

SCSI (0,0,0) (sbd) - 500.1 GB ATA
#1 primary 494.1GB F ext3 /
#5 logical 6.0GB F swap swap

SCSI (0,1,0)( (sdc) - 1.5TB ATA
#1 primary 1.5TB K raid

Then I try to finish partition and write changes to disk and I get the error:

"Identical mount points for two files systems
Two file systems are assigned the same mount point (/): RAID1 device #0 and SCSI (0,0,0), partition #1 (sbd)

please correct this by changing mount points."

Not sure what to change the mount point to on the RAID1 device, or if I have anything else wrong. Any help would be greatly appreciated.