The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

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Amongst link technologies, InfiniBand has gained wide acceptance in the framework of High Performance Computing (HPC), due to its high bandwidth and in particular to its low latency. Since InfiniBand is very flexible, supporting several kinds of messages, it is suitable, in principle, not only for HPC, but also for the data acquisition systems of High Energy Physics (HEP) Experiments. In order to check the InfiniBand capabilities in the framework of on-line systems of HEP Experiments, we performed measurements with point-to-point UDP data transfers over a 4-lane Double Data Rate InfiniBand connection, by means of the IPoIB (IP over InfiniBand) protocol stack, using the Host Channel Adapter cards mounted on a 8-lane PCI-Express bus of commodity PCs both as transmitters and receivers, thus measuring not only the capacity of the link itself, but also the effort required by the host CPUs, buses and Operating Systems.Using either the "Unreliable Datagram" or the "Reliable Connected" InfiniBand transfer modes, we measured the maximum achievable UDP data transfer throughput, the frame rate and the CPU loads of the sender/receiver processes and of the interrupt handlers as a function of the datagram size.Performance of InfiniBand in UDP point-to-point data transfer are then compared with that obtained with analogous tests performed between the same PCs, using a 10-Gigabit Ethernet link.

Abstract-We report on measurements performed to test the reliability of high rate data transmission over copper Gigabit Ethernet for the LHCb online system. High reliability of such transmissions will be crucial for the functioning of the software trigger layers of the LHCb experiment, at the CERN's LHC accelerator. The technological challenge in the system implementation consists of handling the expected high data throughput of event fragments using, to a large extent, commodity equipment. We report on performance evaluations (throughput, error rates and frame drop) of the main components involved in data transmission: the Ethernet cable, the PCI bus and the operating system (the latest kernel versions of Linux). Three different platforms have been used.

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