You can have RAID1 configuration done by software. Before the installation process, you should create another file called ipbrick.cfg in the pendrive root path. Next, the structure is presented along with the explanation:
CONFIGSOFTRAID=1 -> Activates the software RAID SOFTRAIDHDD[0]="sda" -> It's the disk 1 device SOFTRAIDHDD[1]="sdb" -> It's the disk 2 device SOFTRAIDPARTSUF="p" -> Do not change! RAIDTYPE=1 -> It's the RAID type. Only this raid type is supported!
You should know specifically the correct designation of hard drives devices before the file creation, which depends of the used technology: IDE, SCSI, SATA etc.