Home > Storage > PowerScale (Isilon) > Product Documentation > Data Efficiency > PowerScale OneFS Small File Storage Efficiency for Archive > Overview
Customers, such as those in the healthcare industry, often have datasets that are increasingly dominated by small files.
Archive applications such as next generation healthcare Picture Archiving and Communication Systems (PACS) are moving away from housing large archive file formats (such as .tar and .zip files) to storing the smaller files individually. To directly address this trend, the OneFS operating system includes Storage Efficiency feature. This feature maximizes the space utilization of a cluster by decreasing the amount of physical storage required to house the small files that often consist of an archive, such as a typical healthcare DICOM dataset.
Efficiency is achieved by scanning the on-disk data for small files and packing them into larger OneFS data structures, known as shadow stores. These shadow stores are then parity protected using erasure coding, and typically provide storage efficiency of 80% or greater.
OneFS Small File Storage Efficiency is specifically designed for infrequently modified, archive datasets. As such, it trades a small read latency performance penalty for improved storage utilization. Files obviously remain writable, since archive applications are assumed to periodically need to update at least some of the small file data.