The first disk-based custodial storage for the ALICE experiment

Abstract

We proposed a disk-based custodial storage as an alternative to tape for the ALICE experiment at CERN to preserve its raw data. The proposed storage system relies on Redundant Array of Independent Nodes (RAIN) layout – the implementation of erasure coding in the EOS storage suite, which is developed by CERN – for data protection and takes full advantage of high-density Just-Bunch-Of-Disks (JBOD) enclosures to maximize storage capacity as well as to achieve cost-effectiveness comparable to tape. The system we present provides 18 PB of total raw capacity from the 18 set of high-density JBOD enclosures attached to 9 EOS front-end servers. In order to balance between usable space and data protection, the system will stripe a file into 16 chunks on the 4-parity enabled RAIN layout configured on top of 18 containerized EOS FSTs. Although the reduction rate of available space increases up to 33:3% with this layout, the estimated annual data loss rate drops down to 8:6 × 10−5%. In this paper, we discuss the system architecture of the disk-based custodial storage, 4-parity RAIN layout, deployment automation, and the integration to the ALICE experiment in detail.