Another POC to consider for backup. Adding in a configuration setting where, if more than N% of the file has changed, then instead of copying one block at a time, WiredTiger directs the caller to copy the entire file.

Although that would mean copying more data, it could be much more efficient to take a file snapshot, or copy (or hard link) the file once rather than walking and copying individual blocks for nearly the entire file.

This configuration would be off, and the setting would be a percentage of the file.