SAN vs. NAS: What You Need to Know About Data Storage Networks

When building a storage network, your basic decision is SAN vs. NAS. This choice will impact how you access your data. You have to think about your speed requirements, size, remote locations, security and flexibility.

Picking the network that is right for you is critical to providing the right level of capability without overburdening your business. The hardware you choose doesn’t define your network options. However, matching speed and capacity criteria with both choices allows you to maximise your returns on both investments.

This article explains the basic of SAN vs. NAS, and your options for SAN connectivity – TCP/IP, WAN, Fibre Channel, iSCSI and FCoE.

SAN vs. NAS: Two Ways to Connect Your Data

DAS [Direct Attached Storage] is the simplest storage solution. It is a great option for small/micro businesses. However, it is basically an external hard drive. Importantly, there is no network capability. It is just cheap and simple. It can be either SSD or HDD hardware, just like your SAN or NAS network.

NAS [Network Attached Storage] is the next level up. This offers remote access to file sharing and scalability. A NAS uses TCP/IP networking – meaning it goes through your router. It, therefore requires limited infrastructure investment and has great flexibility when communicating between remote locations, but has limited network connectivity speeds.

Functionally, NAS can be configured to operate as a private cloud. It allows your business to centrally store data, access that data from different workstations (or remotely) and easily allow file sharing between different operating systems.

NAS generally uses file level storage. This means that the data is presented in the same format to both the system storing it and system retrieving it. This is great for basic usage but is limiting in large and complex networks.

SAN [Storage Area Network] is the premium solution. It provides a dedicated network capable of moving large chunks of data between different servers and devices with a high level of speed and security. The primary difference between a SAN and NAS is their connectivity infrastructure and how other devices communicate with them. Basically, SAN operates over a dedicated network which increases speed and reliability.

In contrast to NAS file level storage, SANs operate using block level storage. Block level storage allows data to be segregated into blocks or LUNs [Logical Unit Numbers]. These blocks can be controlled as individual virtual hard drives, but are still part of a single pool of resources. You can connect multiple servers to your SAN, designate particular tasks or access capabilities, and still use excess capacity from any given server to aid processes undertaken by separate servers.

• SANs are optimised for hosting virtual machines or other special applications because of the ability to segregate demands on processing power and accommodate multiple formatting systems.
• SANs maximum scalability, flexibility and the utilisation of resources in a large enterprise-level environment. However, they cost more to set up and are more complicated to manage.

SAN vs. NAS: The Network Infrastructure That Makes SAN the More Complicated Choice

How to Hook Up a SAN

Fibre Channel & iSCSI [“iScuzzy”] are your two basic options for connectivity. Fibre Channel [FC] is the older and dedicated solution. It is hard to beat from a quality standpoint – having been built from the ground up to handle storage traffic. However, it has always been expensive and requires purchasing dedicated switches.

iSCSI essentially refers to using ethernet network switches and infrastructure to connect servers to your SAN. iSCSI has been around since the early 2000s, but only more recently has the hardware been able to deliver on the promises.

iSCSI still lags behind FC’s performance potential and inherently places more demands on your server’s processor. This is because of the need to run on top of TCP/IP protocols and requiring the server’s processor to generate storage commands. However, when implemented properly (with 10Gbps Ethernet links on over-provisioned servers) the difference is almost negligible.

However, 10Gbps ethernet cabling and switches are not cheap either. For small businesses with low demand, even using 1Gbps cabling can be a cheap and easy solution to setting up a SAN. It is just going to be slower.

FCoE (Fibre Channel over Ethernet) is the newcomer. Like iSCSI, it runs over multipurpose ethernet infrastructure. However, FCoE uses its own protocol, rather than sitting on top of TCP/IP. Basically, it generates less code and is therefore faster. However, it can’t be routed over WAN – requiring a bridge to connect remote locations.

What Infrastructure Choice is Best for Your SAN?

FCoE is the complicating factor in decision making. iSCSI has generally be considered the cheaper and more accessible option for small businesses, while FC has been the premium enterprise solution. However, the growing prevalence of 10Gbps ethernet cables are somewhat nullifying the need to invest in FC for all but the most I/O heavy environments. Conversely, the flexibility of FCoE is undermining the cost benefits of using iSCSI.

The problems with FCoE are mostly centred on expertise. FCoE uses many of the same specialised management tools as FC that may be unfamiliar to those not already operating FC infrastructure. But, extending your FC network with FCoE requires extra steps to connect the different types of physical infrastructure.

FC still remains the premium solution – but, creative use of iSCSI and FCoE are certainly viable and cheaper options. FCoE over 10Gbps ethernet may very well be the future and best bet for many businesses.

• Fibre Channel is the dedicated and premium solution
• iSCSI has become increasingly accessible and powerful as higher performance ethernet cabling has entered the market
• FCoE is the newcomer that looks likely to swing the balance in favour of existing 10Gbps ethernet infrastructure.

FCoIP (Fibre Channel over IP) is another option to be aware of. However, it is generally used in a limited capacity to cheaply link FC SANs across multiple locations using a TCP/IP network. It is almost never used as a local system because of high latency.