Storage Mastery: DAS vs. NAS vs. SAN

Editor's note: This is the second post in a blog series by CBT Nuggets trainer Anthony Sequeira that will cover IT storage technology.

Isn't it great to have options in life? In IT storage we certainly have options. But it was not always that way. For example, during the early stages, it was only really Direct Attached Storage (DAS) that was used. This method still possesses so many advantages, that it will most likely be part of your storage strategy today. In fact, when it comes to the three types of approaches to IT storage this post will cover, you might just find yourself taking advantage of all of them.

Direct Attached Storage refers to connecting the storage internally or externally to the device that needs it. The key is whether it is inside the device or sitting right next to it; it is a direct attachment through a proprietary or standard interface (such as SATA). Simplicity and speed are certainly part of the advantages here, but as you might guess, scalability is a huge problem.

You start to run out of direct attached storage and you collide with limitations on the number of devices you can connect, and the distance from the device you can move the storage. Engineers often grimace about DAS when they consider the "islands" of storage throughout the organization that they must try and manage.

Network attached storage (NAS) began an explosion onto the scene as networks themselves were improved dramatically thanks to advancements in switches and media in the Local Area Network (LAN).

With the NAS, you have a file server or a specialized NAS device that connects to the network and serves up files to any clients that might need them. In the Windows world, the Common Internet File System (CIFS) is often used for this purpose, while in the UNIX world, it is often the Network File System (NFS). NAS devices might use their own specialized technology to attempt to reduce complexity or expand upon performance.

But even the NAS approach will suffer issues when very large amounts of data are involved, or the very highest levels of performance and availability are required. Enter the Storage Area Network (SAN). The idea here is that the traditional I/O storage needs are combined with the network plumbing itself.

This leads to high-end storage environments that can include servers, mainframes, workstations, disk arrays, disk drives, tape drives, automated tape libraries, and many other types of I/O devices. Virtualization within the SAN allows amazing flexibility and scalability within the SAN system.

For the longest time, Fibre Channel ruled the SAN. Today, powerful alternatives are presenting themselves, with one of the most exciting being Fibre Channel over Ethernet. That sounds like an excellent topic for an upcoming post in this series/

Thank you for reading, and I look forward to your comments below.