performance improvements in a large scale virtualization system

This work shows the optimizations we have been investigating and implementing at the KVM virtualization layer in our research institute based on more than a year of experience in running thousands of VMs in a production environment used by several international collaborations. These optimizations increase the adaptability of virtualization solutions to demanding applications like those run in our institute (High-Energy Physics). In particular we will show what is the best solution to share storage space from an hypervisor to the virtual machines running on top of it, trying to avoid problems that modern storage cluster have. We will also show how different the performance can be comparing real and virtual machines, measuring access to computing, storage and network resources, trying to provide hints on server configuration where possible. This work has been driven by the project called Worker Nodes on Demand Service (WNoDeS), developed by INFN, a framework designed to offer local, grid or cloud-based access to computing and storage resources, preserving maximum compatibility with existing computing center policies and work-flows

Study of cosmic ray showers front and time structure with ARGO-YBJ

ARGO-YBJ is a full coverage Extensive Air Shower array located by the high-altitude cosmic rays laboratory of Yangbajing (4300 m a.s.l., Tibet, China). The detector consists of a layer of Resistive Plate Counters covering an area of about 5800 m^2 with 58x62 cm^2 unit cells. This design allows a detailed characterization of cosmic ray showers induced by primaries with energy in the range from 300 GeV up to 100 TeV. A set of well reconstructed data has been used in order to study the shower phenomenology and front structure with high time resolution (1 ns accuracy) and fine granularity. Simulated CORSIKA showers have been used and the detector response is taken into account in detail for this analysis. Several observables have been investigated in both real and simulated data and compared, aiming to derive hints on cosmic ray shower age, energy and mass composition

The status of the ARGO experiment at YBJ

The ARGO-YBJ experiment, located at Yangbajing, Tibet, China, performed by a wide Sino-Italian collaboration, is designed to study cosmic rays, sub-TeV gamma ray sources and GeV Gamma Ray Burst (GRB) emission in the northern hemisphere, by means of detecting small size EAS (Extensive Air Shower) using a full coverage RPC (Resistive Plate Chamber) carpet. The central carpet of the detector is installed and put into operation to date, with 1900 m^2 of the carpet already operating since December 2004. With a trigger multiplicity of ≥60 hits, corresponding to a primary mode energy of 2 TeV, the angular resolution of EAS measurements is < 1 degree for showers with more than 500 recorded hits. We report the preliminary results of data taking performed during 2005: the all-sky survey for gamma ray sources and the search for GRBs, as well as the cosmic ray spectrum up to about 100 TeV. The Forbush decrease of the cosmic ray flux during January, 2005 is observed using the ARGO data