Thanks much. I haven't seen mention of the 1000 SCSI commands per path thing before, I had assumed RR worked on a frame-by-frame. I'll have more followup questions in a few days after I digest the above, but here's one that comes to mind immediately:
Lets say the active SP for LUN number 43 craps out on an Active-Passive array. At some point the ESXi host should detect the failure (if nothing else, during its every-five-minutes SAN scan), and if its doing multipathing then the PSA will revisit the claim rules and make up a new path table or whatever its called. But does the array notify the host? I'm thinking that maybe if its a Fibre Channel SAN, the RSCNs flying around will hit the HBA and hopefully the HBA driver will pass the notification up to the PSA, but I haven't read anything to that effect.