If you're shopping for a NAS, you probably have multiple computers that will need to access and share files. In general, it is nice to have a single point of storage to make backup and data management easier. No matter what type of computers you have (Windows, Mac, or Linux), you will be able to share files stored on the NAS. In most cases, you'll use CIFS/SMB protocols, which is the default that Windows needs -- Macs and Linux PCs also talk the language. However, you are not limited to just the CIFS/SMB protocol. You can also use AFP (Apple Filing Protocol), which is native to the Mac, and NFS (Network File System), which is native to Linux.
Connecting the NAS boxes to your network should be done via a wired Ethernet cable, and each NAS in this roundup should get two Gigabit Ethernet connections. Strictly speaking, you need only one of these links, but by using both, you gain much greater flexibility. You should use them in a fail-over configuration, which means that if one of your Ethernet cables loses signal, the other will take over. You should also "bond" the two connections together to increase throughput or to balance the network load.
NAS shoot-out: Backups and cloud storage Most important when storing all your data on one big box is to make sure it is backed up regularly. If you're using a NAS device to store your data, you must consider backup. You may think that if you back up your PC or Mac to the NAS, you're covered because the NAS has redundant hard drives. This logic goes only so far. If someone steals the NAS box or it is lost in a fire or flood, then all of your data is gone forever. Anyone who owns a NAS needs to consider the value of their data and how they back it up.
The simplest backup option is to plug a USB drive into the NAS to copy the folders and files that are the most critical to your business. All of the NAS boxes I reviewed include USB ports, and most have eSATA ports. Some even have handy buttons on the front for automating these backups. However, if you need to back up multiple terabytes of data, plugging in an external USB is hardly the best option.
Not long ago, you would look to a software solution to perform regular backups of your data to a tape drive. Tape is still a valid solution, and vendors such as Netgear make it clear that they have partnerships with many of these software makers (Symantec, Acronis, and StorageCraft to name a few).