For what its worth I pulled the factory drives out of one of my R4s when they crashed and replace them with 3TB seagate barracudas.
Worked fine for a while, but then I had an instance where promise utility said all was well, but I got a "The disk you inserted is not readable" message upon boot.
Reformat and initialise twice and all is well again. Have lost faith in it being a super safe storage of data.
Im planning to move back to Sata storage via either the Lacie or ATTO.