Challenging the challenge: handling data in the Gigabit/s range

The ALICE experiment at CE RN will propose unprecedented requirements for event building and data recording. New technologies will be adopted as well as ad-hoc frameworks, from the acquisition of experimental data up to the transfer onto permanent media and its later access. These issues justify a careful, in -depth planning and preparation. The ALICE Data Challenge is a very important step of this development process where simulated detector data is moved from dummy data sources up to the recording media using processing elements and data-paths as realistic as possible. We will review herein the current status of past, present and future ALICE Data Challenges, with particular reference to t he sessions held in 2002 when –for the first time – streams worth one week of ALICE data were recorded onto tape media at sustained rates exceeding 300 MB/s. All the experiments installed at the LHC collider at CERN announced out of the usual requirements. Data streams of unprecedented rates and volumes will be established between detectors, computer farms (online and offline) and mass storage systems. A reliable and effective cooperation will be expected from several components, hardware and software, in-house, public domain and commercial. Final objectives: satisfy the initial requirements, allow subsequent expansions and ensure the desired performance with the maximum reliability. The ALICE experiment [1], with its very high-volume data streams, makes no exception to the rule. To guarantee the viability and reliability of the ALICE Data Acquisition, Data Handling and Permanent Data Storage systems, periodic tests are held in collaboration with the ALICE Online and Offline teams together with the CERN central services (Permanent Data Storage, Operating System deployment and support, centralized data repository and distribution, networking) – the so c alled ALICE Data Challenges. In this paper we review the past experiences of the ALICE Data Challenges, the achieved milestones during the current production period and the future plans. 2. ALICE AND THE DATA CHALLENGES