A network-attached storage (NAS) filer consists of one or more disks designed to attach to a network and act as a file server. NAS filers are attractive to small- to medium-sized businesses (SMBs) for several reasons.
What is a NAS filer?
A NAS filer is a device that is in the least expensive class of network-attached storage. It consists of one or more disks in an enclosure with a built-in file server and operating system optimized for the onboard disk storage. The result is a box that connects to your network and serves files to all the computers on it. Unlike direct-attached storage (DAS), which is added to one of the computers, the filer is a dedicated appliance and doesn't have to split its processing power between serving files and providing for the needs of a user. Unlike a conventional file server, a NAS filer is an all-in-one box designed for easy attachment to the network with a minimum of configuration and installation work.
NAS filer costs
Costs for the low-end NAS filer systems, such as EMC Corp.'s Iomega 34337, with a 1 TB drive, start at less than $300 and typically run $200 to $300 per terabyte of storage. The lowest price models, such as the VisionMan VisionVault 500GB Smart NAS Appliance may only offer 500 GB of storage. More typically, the devices will support up to five 1 TB or 2 TB disks.
Although there isn't really a clear line of demarcation between NAS filers and NAS servers, most units above $1,500 (and some below) have combinations of capacity and features. These high-end units tend to have more storage capacity (up to 100 TB or more with external arrays), more powerful processors, more redundancy, more sophisticated storage management tools that better integrate with enterprise level storage management applications and better granularity of management. However, these units have a more complex setup and management. Just how much of all these features, and how much complexity varies with the price. The low-end units typically max out at 10 or so TB of internal storage, although some of the more expensive ones have SCSI ports which allow additional external disk arrays to be attached to the unit to extend the capacity of the NAS filer.
Are NAS filers a good fit for SMBs?
NAS filers are particularly attractive for SMBs not only because of their low prices, but because they are typically very easy to install. In many cases, installation consists of plugging the filer into the network and letting Plug and Play (PnP) automatically identify the filer on the network. Even the more complex entry-level products typically take fewer than 10 minutes to attach to the network. Some products, such as the Western Digital Corp.'s ShareSpace and Seagate Technology's BlackArmor, come with a utility that automatically discovers the device once it is installed on the network. Most filers are managed by browser-based utilities that are installed on one of the computers on the system.
Filers with more than one disk usually support RAID configurations. On filers with three or more disks, the default is often RAID 5, but other options, such as RAID 1 (mirroring), RAID 0 (striping) and JBOD (spanning) are often available. However, a RAID configuration eats up storage capacity, which can be a downside. The extreme example is a RAID 10 (mirroring and striping) configuration where 4 TB of raw storage capacity translates into 2 TB of RAID storage. While more expensive NAS products come with features such as hot-swappable disks and dual redundant power supplies to enhance reliability, many of the low-end filers lack some or all of them.
What to look for in a NAS filer
When looking for a NAS filer, the most important characteristics are capacity and price. Manageability is also important, especially the ability to control user-level access to files and folders. Performance is less of an issue because most of the filers in this class don't have a noticeable difference in their performance.
Most makers of NAS storage offer one or more NAS filers. Some, such as Iomega, specialize in NAS filers. But nearly all major vendors, such as Dell, Hewlett-Packard (HP) Co., Linksys (by Cisco Systems Inc.), Seagate and Western Digital also have offerings, giving users a wide variety of choices.
Keep in mind that there are tradeoffs when using a low-end filer. Perhaps the most noticeable one is the ease of management. While filers generally come with built-in management utilities, they tend to emphasize ease of setup and use over fine granularity in management. They can also be difficult to integrate into an enterprise-wide data storage management scheme.
Like all NAS products, the performance of filers is critically dependent on network load. Unlike a storage area network (SAN), which is a separate network, NAS serves files over the LAN. This can lead to congestion and degraded performance if the network isn't up to the task.
Expansion is also limited, even on the filers which have SCSI ports for external disk arrays. Unlike more expensive NAS filers and gateways, the low-end products generally can't be clustered to improve performance as the demands on the system grow. The limiting factor here is more likely to be the capacity of the built-in server rather than the storage capacity, which can be attached to the box. Beyond a certain point, which is determined by the design of the filer and the demand put on the NAS appliance, you're better off adding additional filers rather than trying to add disk capacity.
Still, these low-end filers provide a fast, easy and inexpensive method of meeting the storage needs of SMBs. Within their limits they can be an excellent choice for adding storage to an SMB, or a workgroup or remote office in a larger enterprise.
About the author: Rick Cook specializes in writing about issues related to storage and storage management.
This was first published in February 2010