This page contains information on the VFD SWMR (Virtual File Driver Single Writer/Multiple Reader) feature that is currently under development.
The SWMR (Single Writer Multiple Reader) feature enables a second process to read an HDF5 file while data is being written to it. However, the current implementation touches most parts of the HDF5 library, presenting significant maintenance issues, and furthermore, offers no guarantees on the maximum time from write to read, which is problematic for some applications.
The VFD SWMR is more modular, minimizing the maintenance issues. It has additional benefits including allowing the HDF5 library to make guarantees for the maximum time from write to availability of data read and the possibility of extending SWMR to NFS and object stores. Please see the RFC for complete details.