What is Direct Attached Storage (DAS)?

DAS is an acronym of Direct Attached Storage and is a storage system where servers are directly connected to the storage device. In DAS, block-level access protocol is used to access data by applications. And in this article, we will know little more about “Direct Attached Storage” and its type.

Some of the examples of Direct Attached Storage (DAS) are tape libraries, directly connected external hard disk, internal HDD of server, etc. Even home personal computers have direct-attach storage in the form of internal HDD.

Direct Attached Storage (DAS)

Direct Attached Storage (DAS) usually found its use at places which require less number of servers/hosts, even though new storage networking technologies are in high demand. This is ideal for small business, departments, workgroups, etc., which do not share information across enterprises.

DAS is used for file serving in Medium-size companies, while larger business use DAS in conjunction with Storage Area Network (SAN) and Network Attached Storage (NAS).

Direct Attached Storage (DAS) is a one to one relationship (1:1) technology while SAN is many to many.

Now we know what is DAS (Direct Attached Storage), so let us understand about types of DAS.

Type of Direct Attached Storage (DAS)

Direct Attached Storage (DAS) is classified into 2 types viz. Internal DAS or External DAS. This classification is done on the basis of the location of the storage device.

Internal DAS

In internal DAS design, the storage device is internally connected to the server by a serial or parallel bus. For high-speed connectivity over a shorter distance, a physical bus is used and this is also one of the disadvantages of the physical bus.

Also, most internal buses can support only a limited number of devices, and they occupy a large amount of space inside the server, making maintenance of other components difficult.

External DAS

In external DAS design, the server is associated directly to the external storage device. In most cases, the connection between the server and the storage device happens over Small Computer System Interface (SCSI) or Fibre Channel protocol (FCP).

Direct Attached Storage (DAS)

External DAS architecture

An external DAS overcomes the distance and device count drawbacks and gives centralized management of storage devices as compared to the internal DAS.

Benefits & Limitation of Direct Attached Storage (DAS)

The main advantage of using Direct Attached Storage (DAS) is its simplicity and low cost. Implementing the architecture of networked storage systems, like NAS and SAN devices, requires more resources, planning, and time.

For a large SAN & NAS network, making a connection and cabling can be more complex along with its maintenance.

As told above most of the PCs and many servers come with DAS already installed. And if you need additional storage, you can directly purchase storage drives and attach it to your server or PC without any complex setup through a cable. The best example of this is external hard disk’s connected to your PC or laptops.

Direct Attached Storage (DAS) requires very less maintenance (nearly zero) and it is also very simple while SAN and NAS arrangements typically require management software for maintenance and may also require monitoring program.

Hope, you like this information about Direct Attached Storage (DAS). If you have any query or feedback about this article, please let us know through your comments and emails, till then keep learning.

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