As per subject.
When converting from RAID-1 to RAID-5 using mdadm, why must a RAID 1 array contain 2 devices and not more than 2 devices? I don't understand RAID strong enough to pinpoint a reason.
Background: My three RAID-1 arrays contain 3 devices each, my goal is to remove one device from two of the arrays, and attach the spare devices to the remaining RAID-1 array. That will leave two RAID-1 arrays with 2 devices each, and the remaining RAID array with 4 devices. The goal is take the 4 device RAID-1 array and convert that to RAID-5. This is not a discussion about which RAID architectures are better or worse, just the process to change a RAID-1 array to a RAID-5 array.