Snapshot Retention, Deduplication, and Reclaimable Capacity: A Factorial Evaluation of Enterprise Storage Policies

Abstract

Snapshot retention and deduplication policies are often tuned independently, although both determine how much provisioned storage can ultimately be reclaimed. A 3×3 factorial experiment examined the interaction between snapshot retention length and deduplication intensity across 270 workload runs representing databases, virtual desktops, document repositories, and engineering files. Capacity consumed, unique-block ratio, reclaimable space, deletion latency, and read/write performance were measured over repeated snapshot cycles. Longer retention predictably increased logical snapshot footprint, but the effect on physical consumption varied substantially by workload. High deduplication reduced physical growth by 28–46% for repetitive workloads but by less than 9% for already compressed data. Shortening retention from 30 to 7 recovery points increased reclaimable capacity by a median of 21%, although gains were smaller where deduplication ratios were high. No meaningful change in median read latency was observed, while snapshot deletion caused brief p99 write-latency increases under the most aggressive policy combination. The results support joint optimisation of retention and data-reduction settings. Policy decisions based solely on logical snapshot size may misrepresent actual capacity pressure and reclamation potential.