1. A system for managing a storage system, comprising: a memory storing instructions; and a processor coupled to the memory to execute the instructions from the memory, the processor being configured to: receive storage system information from a deduplicating storage system that comprises one or more storage units; in response to the storage system information satisfying generation criteria including the deduplicating storage system capacity being above a threshold, determine a storage capacity forecast using a regression analysis based at least in part on fitting a predictive model to historical data of storage capacity usage included in the storage system information, wherein the regression analysis includes selecting, from a plurality of regressions, a best fitting regression based on an R-squared value to forecast a capacity threshold date for each of the storage units, wherein the capacity threshold date forecasts a date the storage unit reaches a total storage capacity threshold; wherein the historical data of storage capacity usage includes data corresponding to total storage capacity used on particular days of a week, and the predictive model includes a first predictive model for a first day of the week and a second predictive model, different from the first predictive model, for a second day of the week; and in response to the storage capacity forecast satisfying a preset capacity criteria, manage files stored on at least one of the one or more storage units based at least in part on one or more file management policies and a ranked list the one or more storage units, wherein the ranked list is ranked according to the forecasted capacity threshold date of the storage unit.