  Traditionally, distributed and parallel transactional systems have been
studied in isolation, as they targeted different applications and experienced
different bottlenecks. However, modern high-bandwidth networks have made the
study of systems that are both distributed (i.e., employ multiple nodes) and
parallel (i.e., employ multiple cores per node) necessary to truly make use of
the available hardware.
  In this paper, we study the performance of these combined systems and show
that there are inherent tradeoffs between a system's ability to have fast and
robust distributed communication and its ability to scale to multiple cores.
More precisely, we formalize the notions of a \emph{fast deciding} path of
communication to commit transactions quickly in good executions, and
\emph{seamless fault tolerance} that allows systems to remain robust to server
failures. We then show that there is an inherent tension between these two
natural distributed properties and well-known multicore scalability properties
in transactional systems. Finally, we show positive results; it is possible to
construct a parallel distributed transactional system if any one of the
properties we study is removed.
