PDL Talk Series
August 13, 2026
TIME: 12:00 noon to 1:00 pm EDT
PLACE: Virtual - a zoom link will be emailed closer to the seminar
Hans Holmberg, Western Digital
Evolving XFS with Zoned Storage Support
Conventional block storage presents a simple abstraction—an array of logical blocks that can be updated in place—but this abstraction is increasingly mismatched with the constraints of modern storage media. The resulting impedance mismatch leads to well-known inefficiencies, including write amplification, over-provisioning, garbage collection overheads, and performance variability. This is no longer a marginal issue: Shingled Magnetic Recording (SMR) HDDs now account for the majority of shipped storage capacity, making sequential-write constraints a first-order concern for system design. Zoned storage architectures address this mismatch by exposing device-level placement constraints to host software. Both SMR HDDs and NVMe Zoned Namespace (ZNS) SSDs enforce sequential writes within zones and require explicit lifecycle management, effectively shifting coarse-grained data placement and cleaning to the host. While this model can significantly improve efficiency and predictability, it also introduces complexity, requiring substantial changes to applications or specialized storage engines.
Zoned XFS explores an alternative point in this design space by incorporating zoned storage semantics into a general-purpose filesystem. By embedding zone-aware allocation, space management, and garbage collection within XFS, it enables existing applications to operate on zoned devices without modification, while still capturing the benefits of host-managed placement.
In this talk, we present the design and implementation of Zoned XFS and discuss the key challenges encountered in reconciling filesystem abstractions with zoned device constraints. We also provide historical context, tracing the evolution from early zoned storage support and application-driven solutions toward filesystem-integrated approaches. Finally, we evaluate the current state of the system and outline open research questions, including opportunities for improved data placement policies, cross-layer optimization, and broader applicability of zoned storage in heterogeneous environments.
BIO: Hans Holmberg is a Senior Technologist in the Emerging System Architectures group at WD, where he works at the intersection of the storage industry, open-source software, and academic research. His work focuses on advanced storage technologies, with an emphasis on zoned storage, filesystem design, and high-performance I/O for large-scale systems. He is an active contributor to the Linux kernel storage stack and one of the architects behind Zoned XFS, enabling efficient use of next-generation storage hardware. He holds an M.Tech in Computer Science and Engineering from Linköping University (LiTH), Sweden, and continues to collaborate closely with both open-source and research communities to advance modern storage systems.
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