Understanding the main differences between direct attached storage (DAS), storage area network (SAN), and software-defined storage (SDS) supplies context for which situations benefit from network attached storage (NAS).
Direct Attached Storage (DAS) — Typically the least expensive option, DAS storage provides block-level storage that can be connected directly, and most commonly, via USB, or eSATA. This differs from NAS in that accessing the DAS unit does not require data transfer over the network. While this configuration provides the faster transfer speeds, only the host connected to by the DAS unit can access it.
Storage Area Network (SAN) — Compared to DAS units, SANs reside on the opposite side of a storage device spectrum. SANs are typically deployed in enterprise data centers as a high-end storage solution. Like DAS, SANs provide block-level storage, however, it resides on its own network, sometimes referred to as the SAN fabric. The SAN and fabric configuration is optimized for high-performance, and complex use cases, and is critical for enabling high availability (HA).
Software Defined Storage (SDS) — Based on the concept of software defined networks (SDN), SDS utilizes software to bring together storage resources from multiple locations. SDS, like SDN, shares the benefits of maximum data storage flexibility, with the ability to handle dynamically changing application requirements. Additionally, SDS creates a centralized control and management of enterprise storage, beneficially, with the ability to create and apply policies across multiple vendors, empowered by automation to enforce such policies