Work out backup size with retention instantly with clear inputs, formula shown and shareable results.
A grandfather-father-son scheme stores one full plus a chain of incrementals per cycle, repeated for the retention depth. Incrementals are small — daily change times full size — so most storage goes on repeated fulls. Recovery points are what retention actually buys, and restoring from a long incremental chain takes proportionally longer.
Backup storage
incremental = full x daily change; per cycle = full + incrementals x incremental; total = per cycle x fulls retained
Because a corrupted full breaks every incremental that depends on it. Multiple independent fulls limit that blast radius.
The backup system merges a previous full with subsequent incrementals to create a new full without re-reading the source, which saves both backup window and source load.