Most external hard drives are "direct-attached storage," connecting to a single computer with a cable. Network-attached storage (NAS) drives, by contrast, hook up to an entire network of computers via a gigabit Ethernet cable. Some simply function as servers on which files can be backed up and shared, while others serve as hosts for a variety of business and entertainment purposes. Many NAS drives can contain multiple disks, which can be configured as a redundant array of independent disks (RAID). There are several ways to use RAID. You can either combine the capacity of several drives to give you the greatest possible bandwidth for copying files, or you can store multiple copies of the same data on different disks, so you always have a backup if one disk fails. With enough disks on one drive, you can do both at the same time.
The biggest, fastest, best multi-drive NAS available, according to reviewers, is the Synology DiskStation DS1513+ (Est. $780). This drive's five disk bays can accommodate disks of up to 5 TB each, for a maximum capacity of 25 TB. The disks don't come with the drive, however; you'll have to buy them separately, choosing the particular brands and sizes you want from a list of compatible disks. The DS1513+ can support all standard RAID configurations, as well as a special configuration called Synology Hybrid RAID that balances performance across multiple disks of different sizes.
CNET names this Synology NAS an Editors' Choice, awarding it a perfect 5 stars out of 5. Dong Ngo says it combines superb performance and capacity with a "robust" web interface that's familiar and easy to use. He's also impressed with its assortment of features, saying it literally "offers everything storage- and server-related for a home or small or medium businesses." His only caveat is that setting up the more advanced features is probably too complex a job for novice users. The Synology DiskStation DS1513+ also receives much praise from owners on Amazon.com for its speed, easy setup, quiet operation and useful features. Negative reviews are rare, but we did find a few reports of drive failures and complaints about rude or unhelpful customer support.
The QNAP TS-469 Pro (Est. $750) is another multi-disk NAS with mostly strong reviews. This four-bay NAS drive earns 4-star reviews (out of a possible 5) from both CNET and PC World, which say it combines great performance with a host of useful features. However, PCMag.com gives it only 3 stars, saying its read/write performance is subpar compared to similar NAS drives in its class. Reviewer Samara Lynn also says its remote access service, called MyCloudNAS, is awkward to set up.
For most home users, professional-grade NAS drives like the Synology and QNAP are probably overkill. A much more affordable option is the WD My Cloud (Est. $180 for 3 TB). While it doesn't offer the added security of multiple drives, reviewers say it has something the average user will value far more: plug-and-play simplicity. According to Ngo, "You literally just need to connect it to the power, hook its network port to a router (or a switch), and you're done." Reviewers also say the drive is fast, quiet and slick-looking, and it offers easy remote access to your files via the Internet. However, owners at Amazon.com are much less enthusiastic, giving this drive only 3.4 stars out of 5 overall. While they like its features and super-easy setup, we saw numerous complaints that its connection is unstable and its performance is sluggish. Also, while most owners had no trouble setting it up, those who ran into problems say WD's tech support is no help at all.