Operational and performance characteristics of flash SSDs have long been
associated with a set of Unwritten Contracts due to their hidden, complex
internals and lack of control from the host software stack. These unwritten
contracts govern how data should be stored, accessed, and garbage collected.
The emergence of Zoned Namespace (ZNS) flash devices with their open and
standardized interface allows us to write these unwritten contracts for the
storage stack. However, even with a standardized storage-host interface, due to
the lack of appropriate end-to-end operational data collection tools, the
quantification and reasoning of such contracts remain a challenge. In this
paper, we propose zns.tools, an open-source framework for end-to-end event and
metadata collection, analysis, and visualization for the ZNS SSDs contract
analysis. We showcase how zns.tools can be used to understand how the
combination of RocksDB with the F2FS file system interacts with the underlying
storage. Our tools are available openly at
\url{https://github.com/stonet-research/zns-tools}