CMS DAQ Event Builder Based on Gigabit Ethernet

The CMS Data Acquisition system is designed to build and filter events originating from approximately 500 data sources from the detector at a maximum Level 1 trigger rate of 100 kHz and with an aggregate throughput of 100 GByte/s. For this purpose different architectures and switch technologies have been evaluated. Events will be built in two stages: the first stage, the FED Builder, will be based on Myrinet technology and will pre-assemble groups of about 8 data sources. The next stage, the Readout Builder, will perform the building of full events. The requirement of one Readout Builder is to build events at 12.5 kHz with average size of 16 kBytes from 64 sources. In this paper we present the prospects of a Readout Builder based on TCP/IP over Gigabit Ethernet. Various Readout Builder architectures that we are considering are discussed. The results of throughput measurements and scaling performance are outlined as well as the preliminary estimates of the final performance. All these studies have been carried out at our test-bed farms that are made up of a total of 130 dual Xeon PCs interconnected with Myrinet and Gigabit Ethernet networking and switching technologies

The 2 Tbps "Data to Surface" System of the CMS Data Acquisition

The Data Acquisition system of the CMS experiment, at the CERN LHC collider, is designed to build 1~MB events at a sustained rate of 100 kHz and to provide sufficient computing power to filter the events by a factor of 1000. The Data to Surface (D2S) system is the first layer of the Data Acquisition interfacing the underground subdetector readout electronics to the surface Event Builder. It collects the 100~GB/s input data from a large number of front-end cards (650) , implements a first stage event building by combining multiple sources into lar ger-size data fragments, and transports them to the surface for the full event building. The Data to Surface system can operate at the maximum rate of 2 Tbps. This paper describes the layout, reconfigurability and production validation of the D2S system which is to be installed by December 2005

FEDkit: A Design Reference for CMS Data Acquisition Inputs

CMS has adopted S-LINK64 (1) as the standard interface between the detector front end readout and the central Data Acquisition (DAQ) system. The S-LINK64 is a specification of a FIFO-like interface. This includes mechanical descrip-tions of connector and daughter board format and electrical signal definition. The hardware/software package described in this paper (FEDkit) emulates the central DAQ side of this interface at the data rate required by the final DAQ system. The performance, integration with the CMS DAQ software framework, and plans for future developments for the DAQ input interface are also presente

The CMS High Level Trigger

The High Level Trigger (HLT) system of the CMS experiment will consist of a series of reconstruction and selection algorithms designed to reduce the Level-1 trigger accept rate of 100 kHz to 100 Hz forwarded to permanent storage. The HLT operates on events assembled by an event builder collecting detector data from the CMS front-end system at full granularity and resolution. The HLT algorithms will run on a farm of commodity PCs, the filter farm, with a total expected computational power of 106 SpecInt95. The farm software, responsible for collecting, analyzing, and storing event data, consists of components from the data acquisition and the offline reconstruction domains, extended with the necessary glue components and implementation of interfaces between them. The farm is operated and monitored by the DAQ control system and must provide near-real-time feedback on the performance of the detector and the physics quality of data. In this paper, the architecture of the HLT farm is described, and the design of various software components reviewed. The status of software development is presented, with a focus on the integration issues. The physics and CPU performance of current reconstruction and selection algorithm prototypes is summarized in relation with projected parameters of the farm and taking into account the requirements of the CMS physics program. Results from a prototype test stand and plans for the deployment of the final system are finally discussed