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Direct Attached Storage (DAS)


The main protocols used in DAS are SCSI, SAS, fibre-channel, and iSCSI. Traditionally, a DAS system enables storage capacity extension for a server while maintaining a high data bandwidth and access rate. A typical DAS system is made of one or more enclosures holding storage devices such as hard disk drives and one or more controllers. The interface with the server or the workstation is made through a host bus adapter (HBA). A DAS system typically offers fault-tolerant design in multiple areas: controller redundancy, cooling redundancy, and storage fault tolerance patterns known as RAID. Entry-level DAS systems most often are made of an enclosure without active components such as controllers, thus access logic and fault tolerance patterns are provided by the server HBA. Such entry-level DAS systems are typically called a JBOD (Just a Bunch of Disk) indicating their lack of storage intelligence.

Middle and top range DAS systems provide embedded controllers. RAID management is off-loaded, and simple non-RAID HBAs can be used, lowering costs. DAS controllers also enable shared storage access, which permits multiple servers (usually no more than 4) to access the same logical storage unit, a feature that is mainly used for clustering. Top range DAS systems share similarities with entry-level SAN systems and may provide simplistic features of LUN expansion and even snapshot capabilities.

Direct Attached Storage


Nexsan Storage


AC&NC Storage

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