NAS or SAN: Is one better for business continuity?

Different storage schemes work best for different companies. These are some of the trade-offs that will have to go into your choice.

 

Unless your business is a small shop with a handful of machines, direct attached storage (DAS) is not going to cut it for backup purposes. Backing up several individual hard drives onto an external disk quickly turns into an IT management nightmare.

If an organization has several machines connected to a LAN, it’s wiser to use some form of network storage, both to simplify data management in everyday life and to simplify backup with automation and fast data transfer. But which storage method lends itself better to backup and disaster recovery,

network attached storage (NAS) or a storage area network (SAN)? There’s no one right answer, and increasingly the best answer is both.

NAS: Cheaper, easier, but less robust

For small and medium businesses with smaller data demands, NAS storage works well, both as a main storage method and as a backup option. Despite falling prices for SAN systems, NAS is still a cheaper option. It’s centralized and simple for IT to manage and fast enough as long as you don’t have massive stores of data. NAS appliances are pretty much plug and play; just connect them and start serving or storing files.

From a NAS appliance, IT can easily back up to a tape drive or another disk. And NAS is a file-based protocol, which enables intelligent file management, unlike with SAN’s data-blocks protocol. Support for common file systems means that users of heterogeneous operating systems have equal access to data. However, NAS has some disadvantages that make it less than ideal for business continuity. First, because data transfer occurs over a LAN, backing up large amounts of data can slow down the whole network and take a toll on everyday tasks. And the same centralization that makes a NAS appliance easy to manage also makes it a single point of failure on a network.

Scalability has long been an issue with NAS, too. Traditionally, increasing capacity with a NAS device means upgrading to a bigger appliance; NAS appliances cannot ordinarily be pooled into one storage entity. However, virtualization technology now makes it possible for an existing NAS to scale into a larger solution and for resources to be pooled into one virtual storage device.

SAN: Speed and scalability at the expense of simplicity

It’s possible to put together a backup and business-continuity solution in a NAS-only environment. But, in many ways, SAN was made for backup. SAN is designed to move large blocks of data from one place to another over a Fibre-Channel or iSCSI connection, making it much faster than NAS. SAN devices can be clustered to provide automated fail-over from one server to another and to avoid a single point of failure.

Devices can mirror one another for redundancy — for example, in the main system and a backup system. Because SAN operates as a separate network from the LAN, it can perform continuous data backup without taxing the whole office network. Finally, because data is recognized on a SAN system by logical units rather than file units, a SAN solution is highly scalable. You can keep pooling more storage together on a SAN or link multiple SANs to backup to a disaster recovery site, even remotely.

So why isn’t every business using SAN for storage and backup? Although prices are coming down with the advent of iSCSI as an alternative to Fibre-Channel connections, SANs are still far more expensive than their NAS counterparts. And although iSCSI is less complicated than Fibre-Channel, SANs are still more complicated to configure and to manage than a plug-and-play NAS device connected to another disk or tape backup.

Another disadvantage is that because SAN data is measured and transferred in blocks, it’s more difficult to manage files intelligently than it is with NAS, and it does not support heterogeneous operating environments. Unless an organization needs extremely high availability for large amounts of data, the cost and complexity of a SAN far outweigh its advantages for many  businesses.

The best of both worlds — combining SAN and NAS

As SAN and NAS become more alike and more compatible, many businesses are opting for a solution that uses SAN and NAS together. NAS appliances with Fibre-Channel or iSCSI connections can be integrated into a SAN, which gives you both the file-serving control and manageability of NAS up front with the backup speed, availability and scalability of the back-end SAN.

Multiple NAS appliances can be clustered on a SAN to enable automated fail-over. Some businesses even combine NAS, iSCSI SAN and Fibre-Channel SAN into an all-encompassing solution. If your organization can afford it, many vendors such as HP offer solutions that combine NAS and SAN,

with either Fibre-Channel NAS devices or a NAS head on a SAN back end. Combination solutions are more expensive than a NAS-only option, but many still provide a lower cost of ownership than a high-end Fibre-Channel SAN.

When choosing a solution that’s right for your business, consider your needs and your budget. A trusted advisor can help you assess how much availability, backup and storage space your business requires and help you assemble a storage system that will keep you going when the unexpected strikes.