Transparent IDE Mirroring Hardware

The Fat Guy asks: "I'm having trouble trying to find a device that may not Is there any 'in-line' device out there that can transparently mirror IDE drives? I have a need for a device that will connect to an IDE bus (ATA 100) and will then connect to 2 separate (identical if need be, but ideally allowing different geometries) hard drives and transparently mirror them (RAID 1). I can not install an IDE RAID controller (no PCI slot in the embedded box), and I can't do software RAID (it needs to be OS independent). Ideally, I'd like something that would even work with an external USB or Firewire drive controller. CRU once made something similar to this for older IDE drives, but it appears that they dropped the product and did not update it for the modern drives. Any suggestions? Am I wasting my (and your) time asking this?" It's an interesting idea. Does anyone know of a technical reason why such a device can't be made if it doesn't already exist?