It is possible that the nature of my system is sufficiently uncommon that the problem I am experiencing is not pervasive in the vast realm of PI Server deployments. My servers are receiving 250K snapshots/sec. After compression, this translates to 80K archive events/sec. We fill a 1Gb archive in appx 30 minutes. Most of this data is C37118 (Synchrophasor). After upgrading to PI Server 2015 R2, there was a large increase in the number of events in overflow queues. And, although this is difficult to quantify in a performance metric, there is overwhelming evidence that archive data is updating several seconds behind real time. Prior to the upgrade, this was not an issue.