Feature: Network-attached storage

You're running out of space on your servers. Appeals to users to free up disk space aren't working. You don't need to install a storage-area network because you're only working with file- oriented, not block-level transaction-based, data. A single-purpose network-attached storage appliance is the answer. NAS appliances are easy to install because they attach directly to the network via an Ethernet connection. The box becomes the focal point for file access, with users' requests for files bypassing the server, improving bandwidth and eliminating bottlenecks. Some issues to look for when buying NAS appliances are scalability, cost, back-up capability, reliability and compatibility with your server operating system.

Analysts divide NAS into three areas based on scalability and cost: entry-level, with up to 300G bytes of capacity; midrange, from 300G bytes to as much as 1.2 terabytes; and enterprise, high-end, which exceeds 1.2 terabytes.The entry-level and midrange NAS market is characterized most often today by Windows-powered NAS appliances - file servers that have a version of Microsoft Windows embedded as their operating system. The advantages of Windows-powered NAS appliances are that they fit into Windows-based networks because they use the Windows Management Interface that network servers do, and they often can be managed with Active Directory tools.

The remainder of the midrange market consists of NAS appliances that use embedded Linux, FreeBSD or proprietary operating systems that use a variety of file access protocols. The advantage to the user is that these NAS appliances can use the protocols found in your network.

If, for example, your network primarily consists of Windows-based servers, you'll want to choose a NAS appliance that supports Common Internet File System, a Microsoft-devised file access protocol. If you have Unix, NetWare or Macintosh servers in your network, you'll want the capability to use Network File System, NetWare Core Protocol, HTTP, FTP or AppleTalk Filing Protocol.

High-end storage, characterized by NAS appliances from Network Appliance Inc. and EMC Corp., often have a series of more robust features such as fault tolerance; snapshot backup; replication of data between sites; and hot-swappable drives, power supplies and fans. While being more expensive than entry-level and midrange arrays, the performance of high-end storage arrays is becoming sufficient for running mission-critical applications such as databases and online transaction processing applications.

The future of NAS is the notion of managing NAS as it proliferates across the global enterprise.

"NAS file services and systems are hot because they address an isolated silo approach that can be consolidated," says Jamie Gruener, a senior analyst with The Yankee Group. "The challenge is how fast can you migrate and move files from one place to another and how quickly can you manage multiple NAS appliances. You look at distributed file services and systems to do that."

Established companies such as Veritas Software and start-ups such as iSilon, Scale8, Sistina Software, Spinnaker Systems and Z-force all are playing in this new segment of the NAS market. The software or hardware these companies make camp on top of traditional NAS and let a number of geographically separated NAS appliances be managed and accessed as a single device, thus streamlining operations and eliminating the latency problems of accessing distributed NAS.

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