Can I migrate Linux RAID1 to RAID5?

[christoph at linuxsoup.com]

David Backeberg wrote:
> Ummm, yes and no, to the question of the raid1 to raid5. You can take away 
> the second member of the raid1, which will make it a degraded raid1, aka, 
> just your data, with no failover. At this point, you're stuck.

> AND... to the best of my knowledge a redhat kernel can't bootstrap off 
> /boot if it's on a raid5. A custom initrd with raid5 kernel support, or 
> your own custom kernel can. Just something to keep in mind

I'm running RedHat FC3, however it seems like you've identified one possible
migration path.  Create a RAID5 set out of three other disks and bind them
to my broken RAID1 (RAID5+1? ;-)  Then break the last remaining slice of the
RAID1 off (leaving just the RAID5) and bring it online in the RADI5 set...  

Hmmm... is this possible?  Sounds outlandish. 

Can I build a RAID5 set having only 2 out of 3 disks, effectively 
identifying one as offline at creation time?  Good Sunday musings...

christoph