The First-level Event Selector (FLES) is the main event selection
system of the upcoming CBM experiment at the future FAIR facility in
Germany. As the central element, a high-performance compute
cluster analyses free-streaming, time-stamped data delivered from the
detector systems at rates exceeding 1 TByte/s and selects data
for permanent storage.
While the detector systems are located in a dedicated CBM building, the
FLES compute resources will be hosted in the central Green IT Cube
data center approx. 700 meters away from the experiment. This demands
single-mode optics and protocols not susceptible to delay. Previous
concepts therefore included an FPGA-based concentrator stage and custom
optical links to the FLES cluster.
Exploiting newest network technologies allows for a more flexible, yet
cost effective design using COTS equipment for the long-haul link. A
FLES entry cluster, placed near the detector, will terminate detector
links in custom PCIe cards. It aggregates processing components and
delivers them via a specially configured InfiniBand network to the main
compute cluster. The network design facilitates flexible staging and
local processing for testing and detector commissioning purposes.
An overview of the FLES entry cluster and network architecture as well
as newest performance measurements will be presented.