** This has not been tested.
Create a ramdisk of required size
Create a Linux software RAID mirror between the ramdisk, and a partition
of the same size.
Mark the physical-disk as write-mostly (reads will go to the ramdisk)
Format it and load data...
On reboot you'll get a RAID1 mirror with 1 failed drive (because the
ramdisk is dead of course). Just recreate the ramdisk and resync.