Understanding Direct Attached Storage (DAS): Evolution, Market Growth, Architecture, and HPC/Cloud Applications

When reviewing the development of storage, Direct Attached Storage (DAS) is recognized as the most primitive and basic storage method, widely seen in personal computers and low‑end servers; common protocols for connecting DAS to hosts include ATA, SATA, eSATA, SCSI, SAS, and Fibre Channel.

DAS was largely abandoned in favor of NAS, SAN, and distributed storage because it is limited to direct connections for up to four servers, lacks advanced features such as snapshots, cloning, and disaster recovery, and depends on host adapter cards (SCSI, SAS HBA, FC HBA) for connectivity.

Why has DAS resurfaced in the era of big data, cloud computing, and the Internet?

Software‑defined storage drives demand for server‑based storage pools, boosting DAS needs.

Rapid data growth creates a surge in cold‑storage requirements.

HPC and X86‑based Internet workloads seek low‑cost, on‑demand scalability, giving DAS a second life.

DAS market size multiplies

Shipment volume of DAS has grown nearly four‑fold from 2011 to 2015, and its share of the enterprise‑class business (ECB) market rose from 7% in 2011 to 14% in 2015.

DAS solutions offer flexible, reliable, elastically scalable, and cost‑effective enterprise‑grade storage, leveraging high‑density designs, 12 Gbps SAS interconnects, and other technologies to meet cloud, virtualization, HPC, backup, and archival workloads.

Major vendors offering DAS

Among leading storage vendors, HP, Dell, and IBM sell DAS products alongside servers; EMC, NetApp, and HDS have limited DAS offerings. Dell’s DAS accounts for about 39% of shipment capacity and 14% of ECB sales, though Dell restricts online ordering for DAS.

DAS architecture overview

DAS products, often called JBOD (Just a Bunch Of Disks), provide raw capacity without storage services or protocols; the attached server supplies those functions. Typical JBOD components include chassis, drive modules, fans, power supplies, cascade modules, and disks.

Most DAS solutions support independent self‑management, in‑band management, and multi‑server failover, allowing one server to manage multiple DAS units.

JBOD improvements

Traditional JBOD faces limitations in link topology, power, cooling, failure isolation, and environment monitoring. To address these, SBOD (Switched Bunches of Disks) technology introduces switching chips that reduce collision domains and arbitration on FC‑AL loops, enabling point‑to‑point data exchange.

Typical DAS products

Vendors such as Supermicro, AIC, Dell, HPE, and Promise provide DAS solutions. Supermicro’s high‑density DAS can house up to 90 × 3.5‑inch drives in a 4U chassis using SAS 3.0 (12 Gb/s) interfaces.

Standard DAS products support mainstream SES commands, in‑band management, and SAS/NL‑SAS interfaces; HP, Dell, and Promise also offer SSD options.

HBA cards, especially LSI 9300 and 9200, are the most common adapters used with DAS deployments.

DAS in HPC

DAS is widely used in high‑performance computing; Dell, NetApp, and DDN provide SAS JBOD solutions. For example, a Dell rack‑mounted SAS JBOD can support two R710 nodes (primary/backup) with dual SAS HBAs and software RAID, delivering simple, scalable, and low‑cost HPC storage.

In these scenarios, DAS relies heavily on the host operating system for I/O, backup, and recovery, consuming CPU and I/O resources but offering strong scalability for HPC, Internet, and emerging applications.

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