Thoroughly knowing the difference between the three prominent types of datacenter storage will help you immensely in job interviews, product pitches and tech conferences.

Server storage is typically stored in one of three different methods. Since each acronym is similar, it is imperative for you to know the stark differences when discussing DAS, SAN and NAS.

What is DAS?

DAS stands for direct-attached storage. Think about the way servers used to be managed. You would buy a 1U or 2U server, pop it in a rack and use the hard disk space or hard disk array present on the server itself. Storage that is directly attached may use the SCSI, SATA or SAS methods to interface with the motherboard of the server. For a long time, administrators were beginning to shy away from using DAS due to the inefficiencies and management overheard. Now that datacenter and server virtualization is picking up steam, DAS is preferred by some administrators for intensive services. A good example of a modern day use for DAS is Microsoft Exchange. Did you know that Microsoft recommends that you setup Exchange using DAS as opposed to SAN or NAS?

What is SAN?

Storage Area Network or SAN is popular in large corporations because SAN is designed to be accessed rapidly from different hosts and applications.  A characteristic of SAN is that it typically uses Fibre Channel, FCoE (Fibre Channel over Ethernet) or iSCSI to communicate with the already present storage networks. A SAN can take multiple different storage mediums found in a datacenter such as SCSI, NAS or DAS and abstract those resources as needed throughout the entire organization. This process takes place using LUNS. These storage networks are broken down into blocks which can be reallocated as needed. Each LUNS is typically allocated to one specific host or operating system. This allows LUNs to facilitate network storage in a robust fashion.

What is NAS?

Network Attached Storage or NAS is pretty self-explanatory. NAS is typically deployed using a datacenter appliance as opposed to being a dedicated computer or server that is configured to store files. This storage device is then plugged into the network and it can be accessed by any type of client regardless of the host operating system. Whereas SAN only sees LUNS, NAS is able to drill down and see specific file names. NAS and SAN can be combined to offer hybrid storage options to datacenter administrators.

The differences between SAN and NAS can be confusing so think of it like this. SAN uses LUNS which are essential blocks of storage space. This space can be formatted with its own file system and treated as an individual drive. With NAS, there is no need to format the file system because any client connecting to the NAS sees the storage as a repository with file names, not a LUNS solution that must formatted and allocated.