A network-attached storage (NAS) gateway is a big investment for a small- to medium-sized business (SMB). Learn about the pros and cons of NAS gateways for SMBs, the features you should look for in a NAS gateway, NAS
gateways vs. NAS filers, and more in this network-attached storage tutorial.
NETWORK-ATTACHED STORAGE (NAS) TUTORIAL: DO YOU NEED A NAS GATEWAY?
A network-attached storage gateway is a step up from an network-attached storage filer, and it can be a big, complicated, expensive step up. A NAS gateway generally costs less and is simpler to install than the equivalent storage area network (SAN), which makes it attractive to many SMBs, while still offering more capacity and expandability than a standalone NAS filer. Essentially a gateway trades a filer's ease of use and (relatively) low cost for more capacity, flexibility and ease of management. For many businesses, that's a tradeoff worth making, but only if you choose the right NAS gateway.
A NAS filer is an all-in-one box containing a specialized file server with integrated storage. It's designed to be quickly and easily attached to a network to add storage capacity. A NAS gateway is a specialized device designed to attach additional storage to the network. It usually doesn't have built-in storage, but it is designed to have storage attached to it. How much storage the gateway is designed to support is one of the classifying factors.
The first thing to understand is that unlike NAS filers, NAS gateways come in many different sizes with differing complexity, features and capacities. Gateways range all the way from simple devices that support one or two external arrays to head ends that can connect what amounts to a complicated SAN with multiple routers and many arrays. Needless to say, prices vary accordingly, from below $10,000 to well up into the six figures.
Editor's Tip: For more information about NAS filers, read this tip on choosing a NAS filer.
Because of the wide range of capacities and other features, NAS gateways are appropriate for everything from SMBs up to enterprise-size networks.
Not only do prices and capacities vary, but features vary widely as well. For example, some vendors, such as NetApp Inc., support data deduplication in the gateway. Others leave data deduplication (if it is wanted) to the array or an independent appliance. Another feature that may or may not be included is support for iSCSI. Overall, their is a wide range of features supported, so it's important to know what your specific storage needs are before you buy a NAS gateway.
Editor's Tip: For more information on iSCSI, read this tip about iSCSI SANs.
The first question you need to answer is how much storage capacity you want from your gateway. To decide this, you need to look at not only your present storage needs, but also estimate how much storage you're likely to need in the next two or three years.
Keep in mind that you want a gateway that can handle your projected maximum capacity comfortably. That is, you want to top out significantly below (say 20% below) the maximum that your gateway is designed to handle. There are two reasons for this. First, estimating future storage growth is notoriously inaccurate and most people find they have erred on the side of too little rather than too much. Second, for performance reasons you want to have some headroom left in your system. NAS gateways generally don't have hard limits in their capacity the way disk arrays do, but over a certain point performance degrades.
When sizing a NAS gateway, it's also important to consider the topology of your storage. This is a particular problem for companies that are replacing a lot of filers tucked away hither and yon in the company with one or two gateways. This kind of consolidation may require a higher capacity than simply serving the equivalent amount of new storage.
Network and bandwidth considerations play a role as well. NAS adds to the load on the network and that has to be allowed for. In fact, you may find it better from a cost and performance standpoint to use two or more lower capacity filers rather than trying to feed everything through a single large gateway.
Needless to say, you need to make sure you've got enough bandwidth feeding into the gateway from the storage to handle the overall system demand. This may preclude using low-cost SATA disks for your storage because bandwidth and performance may suffer. Alternatively, you may want to segment your storage and use a separate gateway to SATA storage for data that isn't in demand and a higher performing gateway with SCSI disks and Fibre Channel connectivity for the data that needs the performance.
Keep in mind too that unlike a Fibre Channel SAN, NAS is file-oriented. If, for some reason, you have many small files on your system, you will load up your NAS faster than you would a SAN. This isn't likely to be a problem unless you've got an awful lot of very small files, say on an email server, but it is a consideration.
Editor's Tip: For more information on capacity planning, read this SearchStorage article on storage capacity planning.
Capacity aside, there are other distinctions between NAS gateways that need to be considered. One of them is to make sure everything is guaranteed to work together. For example, are your storage arrays certified by the vendor to work with your gateway? If there are compatibility issues, between the storage and the gateway, how will they be resolved? A NAS gateway isn't a SAN, but it is sufficiently complicated that you don't want to get caught in the finger-pointing game if there are problems.
You also need to make sure that the NAS system will work with your operating system and applications. This is much less of a problem than it was a few years ago, but it is still worth checking on.
NAS gateways are a big investment for an SMB and may complicate your storage infrastructure. But if you plan carefully, the investment is worth it and may help ease your storage burden in the long run.
Editor's Tip: For more information on capacity NAS gateways and NAS for SMBs, bookmark our special section on NAS for SMBs.
This was first published in October 2010