My nMP(6,1) will not recover from system sleep when three or more Pegasus Promise2 R4 enclosures are daisy chained to it. This will also happen without drives installed. I also tested it with a second nMP at my locate Apple Store replicating the same system lockup. There are no issues when this configuration is connected to a rMBP Thunderbolt 1 port. I have been communicating with Apple Engineering (via Tech support) on this issue for over a month and the cause would appear to be the Promise Pegasus2 enclosures. Promise has not given any feedback to date. I would strongly recommend you stay away from these enclosures if you plan on daisy chaining more than two enclosures on the same port with system sleep enabled.