There are four file space-handling strategies available to users that use these mechanisms:
This strategy has always been available in HDF5 and is the default. The mechanisms used for this strategy are free-space managers, aggregators, and virtual file drivers.
The current HDF5 file space allocation accumulates small pieces of metadata and raw data in aggregator blocks. However, these blocks are not page aligned and vary widely in sizes. The paged aggregation feature provides efficient paged access of these small pieces of metadata and raw data. It accumulates metadata and raw data into well-aligned pages called file space pages. The library defines a default file space page size but a user can set the page size via a new public routine.
See the RFC on this feature for complete details.
With this strategy the library will request space from either the metadata or raw data aggregator depending on the file space type. If the request is not satisfied, the library will request space from the virtual file driver.
The mechanisms used for this strategy are aggregators and virtual file drivers. It does not use the free-space manager.
This strategy will request space from the virtual file driver. The only mechanism used is the virtual file driver. It does not use the free-space manager.