difference between DAS NAS and SAN

difference between DAS NAS and SAN

difference between DAS NAS and SAN

This article will explore the major storage architectures including DAS (Direct Attached Storage), NAS (Network Attached Storage) and SAN (Storage Area Networks), discussing their benefits and tradeoffs. Microsoft Windows storage technologies have evolved over the years to take advantage of new offerings from storage vendors.  Internal disk drives have advanced from a few hundred megabytes to over a terabyte.  The traditional IDE drives have been joined by SCSI and SATA hard disks offering a variety of options when configuring Windows storage.

When considering the different storage options, you need to keep several things in mind.  First, how much storage capacity will you need?  Will you be able to add additional storage on-demand?  How about data availability – will nightly backups suffice or do you need redundant storage arrays?  And finally, how much are you willing to pay for your storage solutions?  The answers to these questions will help you to decide what Windows storage technology is right for you.

DAS (Direct Attached Storage):

A typical DAS system is made of a data storage device (for example enclosures holding a number of hard disk drives) connected directly to a computer through a host bus adapter (HBA). Between those two points there is no network device (like hub, switch, or router), and this is the main characteristic of DAS.

The main protocols used for DAS connections are ATA, SATA, eSATA,NVMe, SCSI, SAS, USB, USB 3.0 and IEEE 1394.

DAS advantages include:

  • High availability.
  • High access rate due to Storage Area Network (SAN) absence.
  • Elimination of network setup complications.
  • Storage capacity expansion.
  • Data security and fault tolerance.

DAS drawbacks include:

  • Data not accessible by diverse user groups.
  • Allows only one user at a time.
  • High administrative costs.

NAS (Network Attached Storage):

An NAS device is a storage device connected to a network that allows storage and retrieval of data from a central location for authorised network users and varied clients. NAS devices are flexible and scale out, meaning that as you need additional storage, you can add to what you have. NAS is like having a private cloud in the office. It’s faster, less expensive and provides all the benefits of a public cloud on site, giving you complete control.

NAS systems are perfect for SMBs.

  • Simple to operate, a dedicated IT professional is often not required
  • Lower cost
  • Easy data backup, so it’s always accessible when you need it
  • Good at centralising data storage in a safe, reliable way

With a NAS, data is continually accessible, making it easy for employees to collaborate, respond to customers in a timely fashion, and promptly follow up on sales or other issues because information is in one place. Because NAS is like a private cloud, data may be accessed remotely using a network connection, meaning employees can work anywhere, anytime.

Scattered storage arrangements will not work for SMBs.

  • Out-of-sync data
  • Reliability and accessibility issues if storage goes down
  • Delays in responding to customer service requests or sales queries

SAN (Storage Area Networks):

Storage area networks (SANs) are the most common storage networking architecture used by enterprises for business-critical applications that need to deliver high throughput and low latency. A rapidly growing portion of SAN deployments leverages all-flash storage to gain its high performance, consistent low latency, and lower total cost when compared to spinning disk. By storing data in centralized shared storage, SANs enable organizations to apply consistent methodologies and tools for security, data protection, and disaster recovery.

A SAN is block-based storage, leveraging a high-speed architecture that connects servers to their logical disk units (LUNs). A LUN is a range of blocks provisioned from a pool of shared storage and presented to the server as a logical disk. The server partitions and formats those blocks—typically with a file system—so that it can store data on the LUN just as it would on local disk storage.

SANs make up about two-thirds of the total networked storage market. They are designed to remove single points of failure, making SANs highly available and resilient. A well-designed SAN can easily withstand multiple component or device failures.

SANs are often used to:

  • Improve application availability (e.g., multiple data paths)
  • Enhance application performance (e.g., off-load storage functions, segregate networks, etc.)
  • Increase storage utilization and effectiveness (e.g., consolidate storage resources, provide tiered storage, etc.), and improve data protection and security.
  • SANs also typically play an important role in an organization’s Business Continuity Management (BCM) activities.


In summary, there are many types of storage solutions that can be used in a Linux environment. The main 3 types consist of DAS, SAN and NAS. The major differences between the types are startup costs, whether the storage is shared or dedicated, and whether additional storage can be added on-demand. Different technologies are also used to connect and control the storage such as SAS, Fibre and iSCSI.

References for further reading: DAS on wikipedia SAN on wikipedia NAS on wikipedia


About the author


jon snow

Jon is a Linux and F.O.S.S enthusiast, an upcoming Linux SysAdmin, and currently a content creator for ERRORHAT who loves working with computers and strongly believes in sharing knowledge.

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