Unified storage (sometimes termed network unified storage or NUS) is a storage system that makes it possible to run and manage files and applications from a single device. To this end, a unified storage system consolidates file-based and block-based access in a single storage platform and supports fibre channel SAN, IP-based SAN (iSCSI), and NAS (network attached storage).
A unified storage system simultaneously enables storage of file data and handles the block-based I/O (input/output) of enterprise applications. In actual practice, unified storage is often implemented in a NAS platform that is modified to add block-mode support. For example, Reldata Inc offers the SANnet universal IP storage system and Network Appliance Inc. offers a unified storage architecture. Numerous other products based on Microsoft's WUDSS (Windows Unified Data Storage Server) have been configured to support both block and file I/O.
One advantage of unified storage is reduced hardware requirements. Instead of separate storage platforms, like NAS for file-based storage and a RAID disk array for block-based storage, unified storage combines both modes in a single device. Alternatively, a single device could be deployed for either file or block storage as required.
In addition to lower capital expenditures for the enterprise, unified storage systems can also be simpler to manage than separate products. However, the actual management overhead depends on the full complement of features and functionality provided in the platform. Furthermore, unified storage often limits the level of control in file-based versus block-based I/O, potentially leading to reduced or variable storage performance. For these reasons, mission-critical applications should continue to be deployed on block-based storage systems.
Unified storage systems generally cost the same and enjoy the same level of reliability as dedicated file or block storage systems. Users can also benefit from advanced features such as storage snapshots and replication, although heterogeneous support between different storage platforms should be considered closely. While experts predict a bright outlook for unified storage products, it is likely that dedicated block-based storage systems will remain a popular choice when consistent high performance and fine control granularity are important considerations.