Direct-attached storage (DAS) is computer data storage that is connected directly to the computer accessing it, such as a PC or server, as opposed to storage that is accessed over a computer network, such as network-attached storage. For individual computer users, DAS comes in the form of a hard drive or solid-state drive. DAS can be deployed inside a server chassis or as an external storage enclosure directly connected to a card plugged into the internal bus of a server. The term “direct-attached storage” is a retronym for storage area network and network-attached storage.
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How does DAS work?
DAS devices are typically connected to a computer via a Serial Advanced Technology Attachment (SATA) interface. In the case of servers, DAS may also be connected using a Small Computer Interface (SCSI), Serial-Attached SCSI (SAS) or other high-speed interfaces. External storage devices may also be connected via USB.
How to access DAS
DAS can only be managed and configured by the computer it’s attached to. Any other device attempting to access DAS will need to communicate with the computer the DAS is attached to. One example is to use a Remote Desktop Protocol (RDP) connection on Windows computers.
Pros of direct-attached storage
There are three primary advantages to using direct-attached storage.
Since the only costs are the storage device itself and any drive enclosure, DAS is cost-effective compared to storage solutions that require hardware and software to run and manage the devices.
Because DAS is attached to the computer that requires the data, read-write speeds is fast. Network connectivity and congestion issues do not directly affect DAS.
Easy setup and configuration
Computer systems supplied with internal DAS are ready for immediate use. External storage can be used as soon as it’s plugged into a port such as a USB port.
Cons of direct-attached storage
Direct-attached storage does have its challenges though.
No central management and backup
While it’s not a problem for individuals or only a few computers using DAS, growing organizations may run into problems ensuring that the data stored on DAS is available and backed up. Availability and reliability become more complicated and costly than arranging redundancy and backups on networked storage devices.
Poor performance possibility
DAS connected to a PC can be slow to share data with other computers on a network. This is due to performance depending on the resources of the host PC. However, the issue is less prevalent when DAS is connected to powerful servers dedicated to storage.
Unlike software-defined storage that has unlimited storage, DAS is difficult to scale because the number of internal drive bays, availability of external ports, and capacity of external DAS is limited. If internal DAS needs to be upgraded, the host computer may need to be shut down during the upgrade.
There are multiple factors that can affect the security of DAS devices. Insufficiently managed user permissions can allow access to unauthorized users while blocking true users from access. Missing security patches and misconfigured systems can lead to open vulnerabilities.
It’s good practice to regularly run audits of user permissions, scan the DAS for unstructured information and to keep up with operating system (OS) and software patches.