1. In a data processing system operating within a distributed storage system (DSS), a method comprising: identifying a data storage threshold value for an amount of data that can be stored within the DSS; tracking an amount of current storage usage for data stored within the DSS; determining whether the current storage usage exceeds the data storage threshold value; in response to determining that the current storage usage exceeds the data storage threshold value, calculating, based on an amount by which the current storage usage exceeds the data storage threshold value, a target number of documents that can be deleted from the DSS, wherein the current storage usage is proportional to a number of stored documents in the DSS, and the stored documents have a same document type; assigning stored documents to a plurality of groups including a set of document categories based on data characteristics of the stored documents, wherein the groups are ordered based on a relative index associated with corresponding values for data characteristics, wherein all of the stored documents assigned to at least one of the plurality of groups can be deleted in order to provide the target number of documents that can be deleted; and deleting all of the stored documents assigned to a selected at least one of the plurality of groups in order to remove the target number of stored documents.