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hen you select a Network Attached Storage (NAS) solution, you want it to meet your storage requirements in terms of capacity, scalability, client compatibility, and performance. You also must integrate the solution into your current management, backup, and security strategies. This Buyer's Guide presents entry-level and midrange NAS devices available in 1TB to 2TB configurations, although many of the listed devices scale to much larger capacities. When you need additional capacity, your environment's rate of growth will be a key factor in the scalability approach you choose. If your organization's storage needs usually increase slowly, you could get away with adding a standalone NAS server or two each year without creating a physical space or device management problem. If your organization's needs tend to increase rapidly, you might want to pay up front for a solution that scales to a greater capacity through the addition of storage enclosures.

NAS devices, which support multiple, simultaneously active file-sharing protocols, are an excellent way to provide storage to mixed-platform environments. The listed devices all offer at least Common Internet File System (CIFS) and NFS file-sharing capabilities. CIFS is an enhanced version of the Microsoft Server Message Block (SMB) protocol, the standard file-sharing protocol in Windows networks; NFS is a typical set of file-sharing protocols in UNIX environments. Many of the NAS devices support file sharing between additional platforms. For example, some solutions support Novell NetWare and Macintosh file sharing through the IPX/SPX and AppleTalk protocols, respectively. If you plan to share your NAS solution between platforms, make sure that the solution you purchase supports the protocols your environment requires.

The Buyer's Guide includes only NAS devices that provide a hardware RAID controller with support for at least RAID levels 0, 1, and 5. Many provide additional RAID capabilities. Initially, you might think that one RAID level will meet your needs, but as new applications and systems begin to take advantage of the NAS server, you'll want the flexibility to create volumes with different RAID levels to satisfy your applications' performance, reliability, and space requirements.

You'll also want to ensure that the solution you purchase won't be a bottleneck in your environment. The number and speed of NICs on the NAS server should well exceed the anticipated throughput needs of the clients that will use the device. If you plan to scale storage through expansion, make sure that you can scale the network I/O components as well. Similarly, depending on your applications, you might find processing power a bottleneck when you scale to meet the needs of additional clients. The bottom line is that if you shop for a scalable solution, make sure the entire solution scales, not just the storage component.

When you estimate the cost of deploying and maintaining a particular NAS device in your environment, consider the effect on your administrators in terms of managing security integration, data backup, antivirus software, monitoring, and maintenance. For example, in Windows environments, Windows Powered NAS appliances inherently have the upper hand in security integration, but vendors of other proprietary and open OS-based NAS appliances are developing better integration with Windows security than is currently available.

Some of these devices have a dedicated SCSI port for connecting a local backup device, which relieves the network of backup traffic between the NAS server and a backup server. Network Data Management Protocol (NDMP) is an open-standard protocol for enterprisewide backup of NAS devices. NDMP provides a more efficient data stream when you back up over a network to NDMP-supported backup hardware than when you use a standard network backup with protocols intended for client/server communications.

Because you must also protect your NAS servers from viruses, look for a solution that offers a protection mechanism that you can update or lets you use third-party antivirus utilities. Also, make sure the solution includes features that let you monitor performance and hardware functionality. In the event of a failure, devices that support hot-swappable, field-replaceable units (e.g., power supplies, disks) help you minimize downtime.