Characterizing Directionally Asymmetric Job-Level Transfer Behavior in HTCondor Clusters: An Empirical Study of Pattern Discovery and Submission-Time Predictability

The network fabric of geographically distributed high-throughput computing (HTC) clusters has become a critical factor in supporting large-scale scientific workflows, yet job-level data transfer behavior in production batch systems remains insufficiently understood. In this paper, we present a measurement and predictability study of HTCondor-recorded job-level transfer behavior using a 14-month production dataset comprising 757,868 real jobs from the geographically distributed HTCondor cluster at the Institute of High Energy Physics (IHEP). Our analysis reveals a pronounced directional asymmetry in recorded job-level transfer behavior when measured by job count: 88.4% of jobs exhibit only input-side transfer, while 92.9% generate zero output-side transfer. By applying unsupervised clustering as an exploratory labeling tool, we derive empirical labels for seven input-side transfer patterns and three output-side transfer patterns, revealing both dominant low-transfer populations and rare high-transfer groups. We further use lightweight job information available at submission time to examine whether these discovered transfer patterns can be predicted before execution. The results show that input-side transfer patterns are partially predictable from job semantics such as job type, accounting group, and command-line arguments, while output-side prediction is largely constrained by severe class imbalance and dominant job-type regularities. Overall, the results provide empirical evidence that job-level transfer behavior in a real geographically distributed HTC environment is structured, directionally asymmetric, and partially predictable before execution. These findings offer lightweight transfer-awareness signals for future studies of data-locality-aware site ranking, cache preparation, storage layout planning, and transfer-aware resource management in large-scale HTC systems.