The increasing size and complexity of scientific datasets present significant challenges for data management at exascale. This presentation examines the potential of HDF5's subfiling feature, a key component of HDF5, to address these challenges. We will explore the concept of subfiling, explaining how it enables efficient access at exascale. The presentation will also demonstrate real-world use cases where subfiling can significantly enhance I/O performance. We will discuss how subfiling can optimize data access patterns for exascale applications, resulting in faster read and write operations and decreased overall processing time. Additionally, we will analyze the performance benefits of subfiling compared to traditional HDF5 access methods.