Originally published 2 Sept 2009. Updated 20 August 2011
If you don't want (or care) to get into the details behind what makes a NAS tick and just want a short list of candidates to consider, then this article is for you. If you want a more complete guide to choosing a NAS, then read How To Choose the Right NAS for You. (That one hasn't been updated yet, though.)
What They All Do
Let's first list the things that all NASes support:
File Sharing - All NASes provide the basic function of networked storage—just like your computer does when you enable file sharing. But NASes have their own little computers in them and so use much less power, take up much less space and generate much less heat.
Client Backup - If you can read and write to a NAS, then a backup program can too. Some NASes come bundled with one or more licenses for a backup utility—usually for Windows machines. But if the NAS you're considering doesn't come bundled with a backup client, there are plenty to choose from.
Note that some bundled clients aren't very flexible or careful about how they load down your system when they run. So you might end up having to buy a backup program anyway. So don't let the presence or absence of a backup client affect your buy decision.
Ethernet Connection - All NASes also connect to a LAN via Ethernet. Gigabit Ethernet (10/100/1000) is now the rule vs. the exception. But not all NASes with Gigabit LANs support jumbo frames. Lack of jumbo frame support isn't really a biggie. My current NAS test setup that uses an Intel Core 2 Duo machine with RAID 0 array and PCIe Gigabit Ethernet frequently shows little performance gain using 4K jumbo frames and many times actually shows decreased performance!
SMB / CIFS support - The lingua franca of networked filesystems is SMB / CIFS, which is supported by most modern OSes thanks to the work of the open source Samba project. This means that a NAS will work with Windows, Mac OS X, Linux, etc.
The other main network file systems are NFS and AFP, which not all NASes support. Unless you're a 'nix user, you don't need to worry about NFS. You might want AFP support if your Macs are still using OS 9 or earlier.
Note that the internal drive format used does not matter! Clients don't know anything about how a NAS internally stores its data. The only thing that matters to the client is the network file system / protocol. And here, SMB/CIFS is king.
Web browser-based administration - As with most consumer networking products, NASes are administrated through browser-based interfaces. The main gotcha is that products tend to come with Windows-only utilities that help you initially find the NAS and change its IP address to match your LAN.
So if you're not running Windows, you may need to probe around a bit to find your NAS' initial IP address. Fortunately, most NASes come set to automatically acquire their IP address settings via DHCP, which reduces the range of possible addresses that you'll need to check. In most cases, you can log into your LAN's router and find the NAS' IP address in the DHCP client list.
Expansion via USB 2.0 - All NASes have one or more USB 2.0 ports. Among other functions, these ports can be used to connect a USB hard drive, which can be used to back up the NAS internal drive or be shared on the network. Some NASes also throw in faster USB 3.0 or eSATA ports to support those faster drives.
Multiple User Accounts - With few exceptions, all NASes let you create multiple users and assign password protected (or not) storage space for them. You can also set up "Public" folders that all users can access without a password.
NOTE! Just because you can set up Users doesn't mean that you can set up Groups. If you need this feature, be sure to check the NAS specs and features carefully.
Diskful or B.Y.O.D.
A key decision that will narrow your selection field is whether to buy a NAS that comes with hard drive(s) installed (diskful) or without (Bring Your Own Drive).
Diskful NASes are generally cheaper than BYOD, especially single-drive models. The main downside is that when the internal hard drive dies, replacement is usually a factory-only option. One year warranties might tip your decision toward BYOD models. But the three year warranties like those on multi-drive Buffalo and NETGEAR ReadyNAS products, might make it worth choosing a diskful model.
Bring Your Own Drive (BYOD) NAS' key advantage over diskful models is easy drive replacement, because they must have the ability to format and install whatever files are needed on any raw drive. Many multi-drive RAID NASes also let you start with a single drive and then add more drives as your storage needs grow.
But, again, you need to look carefully at product specs. If you are seriously considering the start-small-and-grow approach, I recommend you download the user manual of any prospective buy and read through the details of its RAID migration and expansion features. RAID migration isn't usually supported among all volume configurations. RAID expansion also is very time consuming and requires a volume resync after each drive is replaced. A four-drive RAID 5 expansion can easily take over a day using 1 TB drives. And unless you're dealing with a RAID 6 volume, every second that an array is resyncing leaves you open to losing all your data.
Finally, you can't necessarily throw those old drives that you have sitting on a shelf into your new NAS. For best performance and reliability, you should stick to drives chosen from a product's supported drive list. See Is That an Approved Drive In Your NAS? Or Are You Happy To Risk Your Data?
Single Drive or RAID
The next key fork in the decision road is whether to choose a single drive or multi-drive RAID product. The RAID vs. No-RAID decision is not about data security! It's primarily about how much capacity you want in a single physical box.
You should never trust your precious data to a single device, no matter what RAID level (0, 1, 5, 6, 10, etc.).
RAID is not backup!
RAID was created to enable the construction of large storage arrays out of relatively inexpensive hard drives, using redundancy to compensate for the relatively short life of hard drives. RAID 5 and 10 arrays should be able to withstand the loss of a single drive without losing your data and RAID 6 should be able to lose two drives. But no RAID array will guarantee against data loss if the power supply or controller board fails, or the unit is physically damaged or stolen.
My strong advice it to not use RAID if your storage needs are below 3 TB; stay with single-drive products. If you need more storage, you can always add another NAS and probably still come out ahead for cost.
It might seem strange seeing this topic so far into the article, since some NAS buyers place performance above almost all other criteria. But many NAS shoppers agonize over the choice, when, in fact, other factors can make it moot.
The key performance criteria for NASes are read and write throughput. Throughput is affected by three things: NAS performance; Client performance; and Network speed. If the client or network connection is slower than the NAS, then you won't be able to get the full benefit from a very high-performance NAS.
NAS Performance is primarily determined by processor platform, then internal OS and filesystem used. What generally doesn't matter is the performance of the hard drive used. Hard drive access time, seek time, etc. are generally masked by the overhead of moving data across a network.
NAS RAM size helps only if the file size being read or written is smaller than the RAM size. So if you copy a lot of 1 GB ripped DVD VOB files, then you'll want a NAS with at least that much RAM. But generally, unless you are frequently writing and reading a lot of small files, RAM size won't matter much.
Client Performance is influenced by the same factors that affect NAS performance, i.e. processor, RAM and OS. I've found that a simple switch from Windows XP to Vista SP1 (or Windows 7) can make a huge difference in performance if you have a high performance NAS. How To Build a Really Fast NAS - Part 6: The Vista (SP1) Difference has the details.
The client also must have a Gigabit Ethernet adapter (on-board or separate card) that uses the PCIe bus. PCI-based adapters will limit performance to around 500 Mbps (~63 MB/s) due to overhead factors.
Network speed has to be fast enough to not be a bottleneck. For most current-generation NASes, that means a Gigabit Ethernet connection. This is because even inexpensive single-drive NASes can exceed the 12.5 MB/s limit imposed by using a 100 Mbps Ethernet connection.
If you're using a wireless connection, even if it's draft 802.11n, you don't even need to think about NAS performance; the wireless connection will be the limiting factor. This is because you're doing well if you get about 60 Mbps (Megabits/second) from a draft 11n connection, which is 7.5 MB/s (Megabytes/second).
As with routers, buying something faster than your network connection (or client) can support doesn't buy you anything unless you intend to remove those limiting factors. If you're looking at NASes capable of 50 MB/s or higher speeds, you'll really need to ensure that you client is up to snuff. This means dual core CPU, lots of RAM, OS that can use large block sizes for network transfers, PCIe Gigabit Ethernet and fast storage (SSD or RAID 0 hard drives array).
You're now at the point where the easy desicions have been made and where most people get brain freeze trying to pick a NAS. The main hangup is usually described by newbies looking for buying advice as "not wanting to pay for features that I won't use/ don't need". This is usually followed by a laundry list of features that they would like to have.
This need vs. want vs. cost question is one that only you can answer. But it helps to understand the basic platform types that NAS makers are pumping out.
The Econobox is a single-drive NAS that has all the What They All Do features and usually adds some NAS backup and Media serving features. They typically have Marvell processors.
The Compromise is somewhere in between the Econobox and Classic RAID5 and probably the biggest brain-freezer. It can be a single drive, but is usually a two or three drive BYOD with a smorgasbord of features. Processors can be from either Marvell or Intel Atom.
The Classic RAID5 is a four-drive box aimed primarily at small-business users and prosumers that are either convinced that RAID5 provides higher data security or prefer a lot of storage in a single package. It's usually closer to the Kitchen Sink in price and features, differing mostly in the number of drives and less powerful CPU. Processors are usually Intel Atom.
Kitchen Sink NASes are five-drive (and higher) RAID products that make your eyes glaze over while reading their extremely long feature lists, multi-core Intel processors and multi-Gigabyte RAM size They usually also cause sticker shock when you see their price tags.
The Server Killer is a variation of the Kitchen Sink. This is a very attractive target for NAS makers because the boxes they are aiming to displace are Windows Server based Dell servers or high-end NetAPP storage systems, which cost two to three times as much. The changes from Kitchen Sink models usually include rackmount form factor, redundant power supplies, higher end processors, more RAM, more drive bays and ability to support expansion cabinets.
Another way to come at choosing a NAS is to look at it how you'll primarily use it. This is where you have to be really honest about separating the "must haves" from the "would be nices".
General File Storage, Serving, Backup
These needs can be met by any NAS. The deciding factor may be how your prospective purchase handles backing itself up. If you're using a NAS as primary data storage, i.e. the files are not stored on client devices, then NAS backup is crucial.
If primary storage is on client devices and the NAS is the backup, then backing up the NAS is more a matter of recovery time and convenience vs. preventing data loss.
Backup support varies and requires detailed homework to determine whether a product meets your needs. Options include attached, local network, Apple Time Machine and cloud backup services.
Econoboxes usually will back up to an attached USB or sometimes eSATA drive on demand and might also support automatic scheduled backups. Server Killers, Kitchen sinks, Classic RAID5s and Compromises will support both attached and NAS-to-NAS backup, both immediate and scheduled.
In the past, NAS-to-NAS backup usually worked only within a manufacturer's own product lines. This is still the case for Buffalo NASes, but most other manufacturers support backup to and from generic rsync servers in addition to their own customized versions of rsync.
If you want the most flexible NAS-to-NAS and client-to-NAS backup options, get a NETGEAR ReadyNAS. They can do immediate and scheduled backups to and from most anything and have reliable emailed backup reporting. Iomega NASes are the next most flexible, supporting backup to and from SMB shares and rsync servers.
Media Storage and Streaming
These duties can be supported by any NAS if you don't need UPnP / DLNA or iTunes serving. NAS performance of even Econoboxes has risen to the point where the 20 to 40 Mbps (2.5 to 5 MB/s) requirements of 1080p media streams can easily be met for even multiple streams (see Can Your NAS Do Two Things At Once?) . And there are plenty of entry-level NASes that throw in a basic UPnP AV server and usually an iTunes server, too.
If you want media streaming to iPhones / iTouches or Logitech Squeezeboxes, web-based photo viewers / slideshows, or anything else special in the media serving department however, look to Compromises, Classic RAID5s and Kitchen Sinks.
Server Replacement / Special Applications
If you're thinking of retiring a heavily used Windows or open source server, then you need to be looking at the high-end Kitchen Sinks or Server Killers, although there are some good choices in Classic RAID5s, too. But even then, these products have their limits. They might work fine for file serving and backup for small offices of a few dozen employees. But they also might crumple trying to support even a handful of users simultaneously hitting a heavily-used QuickBooks database. We don't test multiple-user performance. So you're on your own here.
So for those of you who just skipped to the end, hoping to find a list a "recommended" products, I'm sorry to disappoint you. That's not how we roll here at SmallNetBuilder. If you've read this far, then you have a pretty good lay of the NAS land and need to do your homework. Or you could just skip over to the Popular NAS page and see what other people are researching and buying.
The products below are representative of the various product types and are reasonable choices that general consumers with typical NAS needs should be happy with. I have also tested all of the products and have linked to their reviews for your reference.
Server Killers: We don't really review these. But rackmounts from NETGEAR, Thecus, QNAP, Synology and Iomega fall into this group.
I'm sorry that this article came out longer than I wanted. But I guess that's a reflection of the rich choices available in today's NASes. But no matter which selection method you use, you'll find our NAS Charts and NAS Finder to be an invaluable aids in your search. And, of course, our in-depth product reviews are also a great source to tap. So go forth, and get the perfect NAS for you!