Data storage system with automated correction of reference counts in addressing structure to avoid capacity leakage

Abstract

A method in a data storage system includes foreground processes that produce incorrect-high reference counts greater than corresponding numbers of actual references to associated data instances (e.g., virtual large blocks), representing loss of storage capacity. A background process corrects a reference count for a data instance by (1) copying the data instance to a new data instance with an initial reference count of zero and making the new data instance unavailable for reclaiming, (2) scanning a set of referencing structures for all references to the data instance, and for each reference (i) replacing the reference with a new reference to the new data instance, and (ii) incrementing the reference count of the new data instance, and (3) upon completing the scanning, making the new data instance available for eventual reclaiming based on its reference count reaching zero. The process restores reference count accuracy and reduces loss/leakage of storage capacity.