Abstract
ALICE (A Large Ion Collider Experiment) is one of the four major detectors located at the LHC at CERN, focusing on the study of heavy-ion collisions. The ALICE High Level Trigger (HLT) is a compute cluster which reconstructs the events and compresses the data in real-time. The data compression by the HLT is a vital part of data taking especially during the heavy-ion runs in order to be able to store the data which implies that reliability of the whole cluster is an important matter. To guarantee a consistent state among all compute nodes of the HLT cluster we have automatized the operation as much as possible. For automatic deployment of the nodes we use Foreman with locally mirrored repositories and for configuration management of the nodes we use Puppet. Important parameters like temperatures, network traffic, CPU load etc. of the nodes are monitored with Zabbix. During periods without beam the HLT cluster is used for tests and as one of the WLCG Grid sites to compute offline jobs in order to maximize the usage of our cluster. To prevent interference with normal HLT operations we separate the virtual machines running the Grid jobs from the normal HLT operation via virtual networks (VLANs). In this paper we give an overview of the ALICE HLT operation in 2016.
Highlights
ALICE (A Large Ion Collider Experiment, see Figure 1) [1] is one of the four large experiments at the Large Hadron Collider (LHC) at CERN focusing on the study of heavy-ion collisions
During periods without beam the High Level Trigger (HLT) cluster is used for tests and as one of the Worldwide LHC Computing Grid (WLCG) Grid sites to compute offline jobs in order to maximize the usage of our cluster
The ALICE HLT is used as a real time data compression and online reconstruction facility in order to reduce the amount of data which has to be recorded
Summary
View the article online for updates and enhancements. - Flexible event reconstruction software chains with the ALICE High-Level Trigger D Ram, T Breitner and A Szostak. View the article online for updates and enhancements. - Flexible event reconstruction software chains with the ALICE High-Level Trigger D Ram, T Breitner and A Szostak. - The ALICE High Level Trigger: status and plans Mikolaj Krzewicki, David Rohr, Sergey Gorbunov et al. - Commissioning and first experiences of the ALICE High Level Trigger Timm M Steinbeck and the Alice Hlt collaboration. J Lehrbach, M Krzewicki, D Rohr, H Engel, A Gomez Ramirez, V Lindenstruth1,2and D Berzano for the ALICE collaboration
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