High-bandwidth memory (HBM) is regarded as a promising technology for fundamentally overcoming the memory wall. It stacks up multiple DRAM dies vertically to dramatically improve the memory access bandwidth. However, this architecture also comes with more severe reliability issues, since HBM not only inherits error patterns of the conventional DRAM, but also introduces new error causes. In this article, we conduct the first systematical study on HBM errors, which cover over 460 million error events collected from 19 data centers and span over two years of deployment under a variety of services. Through error analyses and methodology validations, we confirm that the HBM exhibits different error patterns from conventional DRAM, in terms of spatial locality, temporal correlation, and sensor metrics which make empirical prediction models for DRAM error prediction ineffective for HBM. We design and implement Calchas , a hierarchical failure prediction framework for HBM based on our findings, which integrate spatial, temporal, and sensor information from various device levels to predict upcoming failures. The results demonstrate the feasibility of failure prediction across hierarchical levels.