NAS Definitions and Benefits
By Thomas Lahive
Users are demanding greater data management from their storage subsystems. In response, subsystems (RAID for example) are taking on more functionality and suppliers are attempting to increase profit margins by adding value to their products. The result of this trend: Network-attached storage (NAS) is becoming an increasingly important technology to increase functionality and potentially lower initial purchase and management costs.
Dataquest defines NAS as a storage system that provides files directly to users without an intervening server, creating independence to application servers, server hardware architectures, and server operating systems. The definition does not include storage servers with operating systems. NAS storage systems are not limited to disk arrays; optical jukeboxes and tape libraries, for example, also fit the definition. As a matter of fact, tape library manufacturers are beginning to embed network protocol support in their products.
Dataquest has identified two types of NAS products, differentiated by hardware design and function:
- Enterprise/departmental NAS systems are external storage devices, which have integrated motherboards that support network protocols. These types of products support enterprise environments with mission-critical or OLTP data. Typical examples include external disk arrays with embedded motherboards or network engines with network protocol support.
- Workgroup NAS systems are external storage devices, each having one multi- function controller that has embedded network protocol support and RAID or other I/O capability. Products in this segment cost less than enterprise/departmental NAS systems, support fewer users, and are marketed as "plug-and-go." A typical example includes a small box that contains several disk drives and a low-cost network engine.
Both categories of NAS devices can be divided into read-only (e.g., CD towers) and write-capable (e.g., RAID) systems.
Currently, the most common way to implement NAS is to bundle a network engine into a RAID subsystem, CD server, or tape library. Another method is to embed network protocols into a storage controller so that one board has dual functions.
For the purposes of analyzing the effect of NAS in the RAID market, Dataquest includes network engines as a separate category. Simply put, a network engine is a low-cost multi-function controller with embedded network protocols and RAID or other I/O capability. Network engines act as bridges between storage devices and networks. Typically, products in this class support Ethernet to the network, and SCSI or IDE to the storage devices.
Server Trends Create NAS Opportunity
Most users do not plan correctly for future server capacity requirements. Typically, capacity more than doubles each year. System downtime and management costs become quite high with the simple addition of a disk drive. And most operating systems require a system reboot to recognize added capacity.
External storage devices simplify this common problem. NAS devices easily accept new capacity and communicate these changes to host servers or end-users. The result: NAS allows users to devote capacity to a specific application or department without having to add additional disk arrays or servers.
At a recent GartnerGroup storage conference, users were informally polled as to what percentage of their Windows NT servers have mission-critical applications. More than 60% of the respondents said that at least one of their applications required 24x7 up-time. RAID only protects data on disk drives; protecting data in the path between clients and storage subsystems is another story. Therefore, eliminating as many components as possible (e.g., the server) minimizes the potential for failure.
Another advantage of NAS is the ability to empower departments and workgroups. Often, certain departments have remote groups that require exorbitant amounts of IT resources. These remote requirements include processing power and storage capacity.
The 84% average growth rate experienced by the NAS market is largely due to the increasing popularity of RAID subsystems with network protocol support--both enterprise and workgroup versions (see table on p. 53). A key demand factor for these RAID systems is the adoption of storage area networks (SANs). A SAN is a network infrastructure designed to connect multiple disk arrays or other storage devices, typically over a Fibre Channel interconnect. The SAN concept has been around for a while in the mainframe market, with ESCON as the standard interface.
With the widespread adoption of Windows NT and the impending demand for clustered servers, demand for shared storage, robust backup, and easier management will increase significantly. The SAN concept supports these functions because RAID subsystems connected to the ring will have network protocol support.
There are three ways to connect a typical subsystem to users: through a host, directly over a network, and via a SAN. When NAS devices are connected to a SAN, they are classified as NAS if network protocol support is loaded on the system. Dataquest predicts that the majority of subsystems that will be attached to SANs will have network protocol support and therefore will be classified as NAS devices.
SAN-connected NAS products, on the other hand, will mostly consist of enterprise solutions because this architecture will probably be managed more closely. LAN/WAN-connected NAS devices will be comprised more of workgroup solutions.
Enterprise NAS products could compete with low-end general-purpose servers. NAS has an advantage over low-end servers if users can offload CPU functionality, increase availability, and simplify the purchase and management of storage. However, the server market is growing so fast that Dataquest doubts NAS will have enough of an impact to change the product strategy of a Compaq, for example, or limit the earnings potential of Microsoft or Intel. NAS benefits the overall storage market because it provides a solution that helps users differentiate the server purchase from the RAID system.
Thomas Lahive is a senior industry analyst, specializing in server storage and RAID, at Dataquest, a market research firm in San Jose. Lahive works in the company`s Westborough, MA, offices. He is a regular contributor to InfoStor.