Online data handling and storage at the CMS experiment
Author(s)
Darlea, G.-L.; Demiragli, Zeynep; Gomez-Ceballos, Guillelmo; Paus, Christoph M. E.; Sumorok, Konstanty C; Veverka, Jan; ... Show more Show less
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During the LHC Long Shutdown 1, the CMS Data Acquisition (DAQ) system underwent a partial redesign to replace obsolete network equipment, use more homogeneous switching technologies, and support new detector back-end electronics. The software and hardware infrastructure to provide input, execute the High Level Trigger (HLT) algorithms and deal with output data transport and storage has also been redesigned to be completely file- based. All the metadata needed for bookkeeping are stored in files as well, in the form of small documents using the JSON encoding. The Storage and Transfer System (STS) is responsible for aggregating these files produced by the HLT, storing them temporarily and transferring them to the T0 facility at CERN for subsequent offline processing. The STS merger service aggregates the output files from the HLT from ~62 sources produced with an aggregate rate of ~2GB/s. An estimated bandwidth of 7GB/s in concurrent read/write mode is needed. Furthermore, the STS has to be able to store several days of continuous running, so an estimated of 250TB of total usable disk space is required. In this article we present the various technological and implementation choices of the three components of the STS: the distributed file system, the merger service and the transfer system.
Date issued
2015-12Department
Massachusetts Institute of Technology. Laboratory for Nuclear ScienceJournal
Journal of Physics: Conference Series
Publisher
IOP Publishing
Citation
Andre, J-M et al. “Online Data Handling and Storage at the CMS Experiment.” Journal of Physics: Conference Series 664.8 (2015): 082009.
Version: Final published version
ISSN
1742-6588
1742-6596