As far as I know, it is true that EMC disks can only replicate between EMC disks, and Hitachi disks can only replicate between Hitachi disks, etc. Each hardware vendor uses its own proprietary protocol to perform this replication. I have never heard anything that would contradict this.
If you need a firmer answer, I recommend contacting each of the hardware vendors directly.
If you have the need to replicate data between hardware arrays from
different vendors, you need to contact a company like VERITAS or Legato, and
use one of their host-based replication products.
This was first published in April 2003