The CMS Event Builder
V. Brigljevic, G. Bruno, E. Cano, S. Cittolin, A. Csilling, D. Gigi,, F. Glege, R. Gomez-Reino, M. Gulmini, J. Gutleber, C. Jacobs, M. Kozlovszky,, H. Larsen, I. Magrans de Abril, F. Meijers, E. Meschi, S. Murray, A. Oh, L., Orsini, L. Pollet, A. Racz, D. Samyn

TL;DR
This paper evaluates architectures and technologies for the CMS experiment's event builder, focusing on throughput, scalability, and implementation options using test-bench measurements and simulations.
Contribution
It presents a detailed study of a two-stage event builder architecture for CMS, including performance evaluations of Ethernet and Myrinet interconnects.
Findings
Ethernet protocols achieve significant throughput with Layer-2 and TCP/IP.
The two-stage architecture scales linearly with the number of second-stage switches.
Test-bench results demonstrate the feasibility of the proposed event builder design.
Abstract
The data acquisition system of the CMS experiment at the Large Hadron Collider will employ an event builder which will combine data from about 500 data sources into full events at an aggregate throughput of 100 GByte/s. Several architectures and switch technologies have been evaluated for the DAQ Technical Design Report by measurements with test benches and by simulation. This paper describes studies of an EVB test-bench based on 64 PCs acting as data sources and data consumers and employing both Gigabit Ethernet and Myrinet technologies as the interconnect. In the case of Ethernet, protocols based on Layer-2 frames and on TCP/IP are evaluated. Results from ongoing studies, including measurements on throughput and scaling are presented. The architecture of the baseline CMS event builder will be outlined. The event builder is organised into two stages with intelligent buffers in…
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Taxonomy
TopicsAdvanced Data Storage Technologies · Parallel Computing and Optimization Techniques · Distributed and Parallel Computing Systems
