  Heterogeneous systems consisting of general-purpose processors and different
types of hardware accelerators are becoming more and more common in HPC
systems. Especially FPGAs provide a promising opportunity to improve both
performance and energy efficiency of such systems. Adding FPGAs to clouds or
data centers allows easy access to such reconfigurable resources. In this paper
we present our cloud service models and cloud hypervisor called RC3E, which
integrates virtualized FPGA-based hardware accelerators into a cloud
environment. With our hardware and software framework, multiple (virtual) user
designs can be executed on a single physical FPGA device. We demonstrate the
performance of our approach by implementing up to four virtual user cores on a
single device and present future perspectives for FPGAs in cloud-based data
environments.
