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Five questions to ask before you buy NAS

Have in mind size, usage requirements

Buying network-attached storage (NAS) should be a simple affair. Here are a few questions to ask yourself before you buy to make sure you're getting what you need:

You may want to consolidate several file servers so you can manage the combined storage better. If you are looking to host DNS and Web services, consider a NAS device with both Common Internet File System and Network File System support and limited storage capacity. If you are hosting engineering or computer-aided design applications, then consider a more powerful NAS system with higher capacities or a clustered NAS system for the large files that the application generates.

If you are looking to use the NAS appliance for consumer storage ? to store video, MP3 and other digital files -- then a smaller, easy-to-install and configure appliance is probably best. Look at such NAS appliances as the Buffalo Technology TeraStation, Adaptec Snap Server, Infrant Technologies' ReadyNAS NV, Anthology Solutions' Yellow Machine P400T, Sabio Digital's CM-4 or Iomega's 400R.

The capacity of NAS devices is important. There's no sense in buying less storage than you will need or more storage than you can ever consume. Take a look at your storage requirements for the next few years and decide what size NAS device you need. NAS appliances come in capacities ranging from 500GB to more than two petabytes.

Look at the changes you need to make to your network infrastructure to accommodate the NAS appliance. Do you need Gigabit Ethernet to support high-speed connections to storage? Do you need to support both file-level and block-level storage-area networking access? Do you need multiple connections to the Gigabit Ethernet network to support high availability and performance?

Backing up and protecting your NAS appliance are as important as storing data on it. Are your NAS appliances in branch or remote offices? If so, you might want to use a product such as HP's OpenView Storage Mirror to copy only blocks of data that have changed at remote sites.

Many NAS appliances come with advanced features built in. But which ones do you need? For instance, do you want to be able to replicate data to another appliance for disaster recovery? Do you want to be able to move data from a NAS appliance so you can upgrade or patch the appliance or applications running on it? Do you need clustering for high availability and fault tolerance? All are points to consider before you buy.