Performance Support

Storage: Comparison of SAN and NAS

TranscriptLet’s discuss the similarities and differences between SAN and NAS. First at the device level, SAN storage devices and NAS storage devices are similar and that they're both effectively standalone purpose-built computer systems consisting of a processing component and an array of disk drives. Both SAN and NAS devices are used to centralize and share storage among multiple heterogeneous computer systems and both promise reduced and centralized storage administration. Note that I'm specifically talking about the storage devices.

Let me clarify, when we speak of SAN at a higher level, the storage area network is not just a storage device but it’s the actual networking component that allows the SAN storage devices to communicate to the computers and to each other. This is a major difference between SAN and NAS since NAS devices simply connect to existing TCP/IP networks much like PCs and servers do. So this added level of infrastructure and complexity is one of the big differences between SAN and NAS. One leverages the existing Local Area Network while the other requires its own dedicated network.

Another difference is that SAN storage is accessed at the block level and NAS devices are accessed at the file level. Block level access for SAN allows the computers connected to the SAN storage to access the storage directly as if the storage were locally attached. The server operating system sees the SAN storage as local disk just as if it were physically installed in the computer itself.

File level access for NAS devices is presented differently. The NAS storage is presented to a computer or server on the network by means of a file sharing protocol and the server operating system sees the storage as a shared file location on the network. Protocols like NFS and CIFSs are used to share storage on the network. SAN storage accesses the disk at a block level and is presented just as if it were local disk to the OS as we see on the left hand side of the screen. NAS storage is accessed at the file level and the disk is presented as if it were file share on the network as displayed in the right hand side.

So when would one choose to implement one over the other? Well that really depends on many factors that are beyond the scope of this discussion, but as a general rule of thumb if SAN or NAS are already deployed and meet the basic needs including cost then it might be best to grow the current deployment rather than implement another solution. If neither SAN or NAS are already in place NAS might be better suited in a situation where there are a group of computers that need to share storage files over the network. SAN might be best suited in scenarios where multiple application servers require access to shared storage for large amounts of data and/or high performance needs for example database servers.

I hope this helps distinguish the similarities and differences between SAN and NAS. Thanks for watching.

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