Thanks Venkatachalam, we ARE using the R8 as a DAS.
We have the first r8 in RAID 5 mode connected to the Mac Mini via Thunderbolt, the Mac Mini will share out the data, that works fine.
We want the 2nd R8 to be a RAID 1 mirror of the first r8, we want the 2nd R8 to be in a different part of the building, so daisychaining via Thunderbolt isn't an option, to gain the distance we are trying to use the SanLink3. Unfortunately when using the SanLink3 the 2nd R8 won't power up.
I'm going to guess that the SanLink3 isn't sufficient to tell the 2nd R8 to power up but the Distributor told us this would work, so while I wait for them to clarify I thought I may get insight here.