Shawn,
Thanks for your reply. This was exactly the document that I was looking for all the the other guides I had found were the advanced ones.
I I am reading this correctly then if we are replicating a 4Tb volume then we need at 3 * size of the primary volume i.e 12Tb of free space for volume plus internal snapshots? Is this at both primary & scondary sites.
Th error message was for the High threshold being breached.
Many Thanks
Allan