Block incremental backup
Also called: block-level incremental, block delta backup
A block incremental backup goes finer than whole files: within a changed file it stores only the individual blocks (pages) that changed, rather than re-copying the entire file. pgBackRest introduced this in version 2.46. It compares block checksums against the previous backup to decide what to store.
What this means
Goes finer than whole files: inside a file that changed, it stores only the individual blocks that changed rather than re-copying the entire file. It compares block checksums against the previous backup to spot the differences. pgBackRest added this in version 2.46.
Why it matters operationally
For a large, mostly-static table, say 500 GB that changes a few pages a day, file-level incrementals would still re-copy whole changed files, but block incrementals capture just the handful of changed pages, shrinking backup size and time dramatically.