“…On the other hand, as the upgrade process of an HPC storage system usually takes a vast amount of investment, time and e ort [7,15,34,47], the total capacity of the scratch space tends to remain xed for a considerably long time after the deployment of a system. Additionally, HPC applications constantly generate a tremendous amount of data [1,2,9,14,[21][22][23]35], making it necessary to manage storage resource e ectively [11,13,18,19,38,48] with, in particular, "data retention" -a process of retaining useful les and purging unimportant les to improve the utilization of storage space.…”