When a file is created or opened for writing using the core virtual file driver (VFD) with the backing store option turned on, the core driver can be configured to track changes to the file and write out only the modified bytes.
This write tracking feature is enabled and disabled with
is_enabled. The default setting is that write tracking is disabled, or off.
To avoid a large number of small writes, changes can be aggregated into pages of a user-specified size,
1 enables tracking with no page aggregation.
The backing store option is set via the function