DAS Meaning & Definition

DAS is short for direct attached storage, a tool used for storing digital data.

What is direct attached storage?

DAS is a storage device that’s attached directly to a machine, such as a PC (personal computer) or a server. This type of storage is an alternative to storage that’s connected to a machine over a network. DAS is standard in virtually all PCs, including desktops, laptops and mobile devices.

How does DAS work?

DAS devices can be connected to a machine both internally or externally. These devices are connected using either a USB (Universal Serial Bus), SATA (Serial Advanced Technology Attachment), PATA (Parallel Advanced Technology Attachment), SCSI (Small Computer System Interface) or SAS (Serial Attached SCSI) port. If other machines need to access the DAS of another machine, it must first communicate with that machine over a network connection.

DAS is in opposition of storage-as-a-service (STaaS), aka cloud storage. STaaS is a more recent development of storage and involves no hardware. Data is instead stored in cloud servers using either internet or network connections.

Types of DAS

The most common types of direct attached storage devices are hard disk drives (HDD) and solid-state drives (SSD).


Hard disk drives, also called hard drives or disk drives, are a mechanism that uses an oscillating mechanical arm to read and write data on a spinning hard disk. These DAS devices have long been the standard form of storage used in PCs and servers. The most common types of connections used for hard drives are SATA, SCSI, and PATA.


SSDs are a more recent development in DAS. This type of storage device has no spinning disk or mechanical pieces. Rather, it uses flash-based memory. When they were first developed, SSDs were primarily used by enterprise organizations to store data on servers and high-end PCs. As technology has advanced, they’ve become more affordable and are more common in standard PCs. SSDs are more expensive than HDDs but they also offer faster read and write speeds and are more reliable as they have no moving parts. Common SSD connections include M.2, SAS, and SATA

Pros and Cons of DAS

Pros of DAS

Because DAS is connected directly to a machine instead of relying on a network or internet connection, it typically performs better than alternatives. They’re also easy to set up. Internal DASs are typically preinstalled or can be installed manually and easily configured. External DASs are usually plug-and-play, sometimes only requiring to be formatted. While STaaS is normally based on a regular subscription, DAS is more affordable, as they only require a single initial purchase.

Cons of DAS

All DASs are all created with a set amount of storage, so they are unable to scale up. They also decrease in performance when shared from one machine to another over a network connection and may slow down the host machine in the process. Unlike most STaaS offerings, DASs do not have native automatic backup systems. This requires an investment in a backup software program.

SAN vs. NAS vs. DAS

DAS is sometimes confused with SAN (storage area network) and NAS (network attached storage), but there are multiple key differences.


SAN storage uses dedicated high-speed networks to transfer data between servers. This type of storage is substantially more expensive than DAS and usually requires the help of storage specialists for management.


NAS uses a combination of hardware storage devices and software. It offers better performance than DAS when sharing data between machines. It can also be scaled up quickly by adding more NAS devices.


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Kyle Guercio
Kyle Guercio has worked in content creation for six years contributing blog posts, featured news articles, press releases, white papers and more for a wide variety of subjects in the technology space.

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