SANs VS. NAS: What You Should Know And Why You Should Care.Though different, they ultimately will merge into Enterprise Storage Networking
SANs and NAS (1) See network access server.
(2) (Network Attached Storage) A specialized file server that connects to the network. A NAS device contains a slimmed-down operating system and a file system and processes only I/O requests by supporting the popular share common objectives: Multiple server storage sharing; simplified storage management; employing network storage to replace direct attached storage; and reducing storage costs. Let's take a look at each to see what they offer and how they compare.
A Storage Area Network (SAN) is a new technology designed to overcome throughput and data-sharing issues that are common in existing data networks. SANs are fully scalable, fault-resilient shared data repositories providing unlimited mixing and matching of storage devices, storage space, and even files (under certain conditions) across the enterprise network. SANs are catapulting to popularity as the architecture of choice for centrally managed network storage tasks. SANs are high-speed, high-bandwidth I/O channels (usually Fibre Channel) that connect to the back end of local area network (LAN (Local Area Network) A communications network that serves users within a confined geographical area. The "clients" are the user's workstations typically running Windows, although Mac and Linux clients are also used. ) servers. They remove cumbersome storage functions off of the server, thus improving overall LAN and WAN performance.
A SAN usually consists of a high-throughput interface (commonly Fibre Channel), interconnects (switches or hubs), and a protocol (IP, SCSI SCSI
in full Small Computer System Interface
Once common standard for connecting peripheral devices (disks, modems, printers, etc.) to small and medium-sized computers. SCSI has given way to faster standards, such as Firewire and USB. , or IBM's ESCON (Enterprise Systems CONnection) An IBM S/390 fiber-optic channel that transfers 17 Mbytes/sec over distances up to 60 km depending on connection type. ESCON allows peripheral devices to be located across large campuses and metropolitan areas. ). A typical SAN includes a blend of storage devices (perhaps automated tape libraries and RAID) capable of communicating with multiple hosts and with each other over a fast, fault-tolerant storage pipeline (the SAN). The SAN is actually a dedicated storage access I/O channel (containing network properties) optimized for handling storage tasks.
Network Attached Storage (NAS) is a LAN-attached storage server with a small, optimized system software package dedicated to performing storage-related tasks. It includes pre-configured disk capacity with the ability to be quickly installed on popular network platforms. If you need to easily expand storage capacity while providing uninterrupted high-performance data access across your LAN, you may want to consider a NAS appliance. When budgets are tight and a quick fix is required, a NAS appliance may be a low-cost, efficient solution to dodge that network-to-storage logjam log·jam
1. An immovable mass of floating logs crowded together.
2. A deadlock, as in negotiations; an impasse.
Noun 1. .
View NAS storage as the building block for creating a network with virtually unlimited server storage capacity. NAS accomplishes this expanded capacity without sacrificing either file access speed or system throughput--which would be affected with network storage add-ons such as tape libraries, CD towers, or optical jukeboxes. Instead, NAS storage devices are usually magnetic disks or RAID arrays that provide seamless high-performance file access and filing by operating at full hard disk speed. And the cost in time, resources, and inconvenience is far less than that of increasing internal storage space within the server or implementing a SAN.
Following is an unbiased discussion of the why(s) and when(s) to build a SAN or add-on NAS capability. We close with a peek at how SANs and NAS may be merged to obtain the maximum benefits of these two powerful storage technologies.
The Case For SAN
The need for the SAN architecture came about due to a jump in software and processor performance during the last decade. The business world took advantage of this newfound gain by shifting from data centers to distributed networks, most of which are Unix and NT Windows-based. Though not without improvements of their own, storage devices have not kept up in terms of performance. The difference is felt particularly at sites that typically handle large volume file transfers such as network backup and recovery or constantly deal with high storage access rates, as networks become sluggish and jammed. However, by integrating a SAN infrastructure into an existing network, storage functionality can be scaled to an equal level with software and processor performance.
By extending the any-to-any connectivity of LAN architectures to storage resources, the SAN makes any data on the network, in any location, accessible through multiple paths to any network user, node, or application. These shared-network storage devices are now multiserver accessible and are no longer coupled by restrictive server-to-individual storage unit connections.
The SAN topology frees all storage and file access tasks from the operational limitations of an individual server and the general traffic constraints of a LAN or WAN. Because a SAN externalizes storage outside of a server, the stored data is made available to multiple hosts across multiple platforms Refers to two or more operating environments, which typically include the CPU family and operating system. For example, if versions of a program run on Windows and the Macintosh, the software is said to support multiple platforms. without imposing a network overhead burden. Incorporating a SAN into the enterprise network environment enhances LAN/WAN LAN/WAN Local Area Network/Wide Area Network throughput and reduces traffic jams, as the TCP/IP TCP/IP
in full Transmission Control Protocol/Internet Protocol
Standard Internet communications protocols that allow digital computers to communicate over long distances. (standard) LAN is freed from large bandwidth-hungry tasks such as data storage and backup, file access, and file retrieval. Immediate performance improvements can be realized in such high throughput, large packet data transfer tasks as data migration, archiving/retrieval, and file read/writes.
The reliability of the storage subsystem The part of a computer system that provides the storage. It includes the controller and disk drives. See storage system. is also impacted because of a SAN's fault-tolerant operation. With a SAN, data is accessible through multiple data paths (such as through dual switches or ports). In this way, redundant access can be easily built in. SAN's inherent centralization cen·tral·ize
v. cen·tral·ized, cen·tral·iz·ing, cen·tral·iz·es
1. To draw into or toward a center; consolidate.
2. benefits simplify administration and management of a network's storage components. This centralization significantly improves backup and restore capabilities, making it easier to scale cost-effectively and achieve disaster protection data copies.
The Case For NAS
The NAS architecture was designed with ease of use and heterogeneous connectivity in mind. NAS can be installed almost immediately to handle additional online storage capacity needs. Yet network response time may be an issue. Storage bottlenecks occur when the business encounters a combination of repetitive file accesses, and large program and data files that strain storage resources. With traditional methods of server attached storage, network traffic jams often result because LAN throughput and application performance is limited by the time it takes to read or write across the network. The fundamental issue causing this condition is storage response time (i.e., the time it takes users to gain access to data).
When response to multiple users' requests become "snail-paced," it causes frustration, dissatisfaction with the network (and those associated with maintaining it), and affects the company's ability to serve its customers. NAS devices tackle this problem by providing additional storage capacity at local magnetic hard disk speed across the network. These dedicated NAS devices allow consolidation of multiple traditional file servers into one easy-to-maintain-and-administer unit that is logically attached to multiple subnets or the main network.
NAS provides easily expandable, highly reliable additional storage without requiring network interruption to install. For the MIS professional, this solution comes without the problems usually encountered when increasing server disk capacity--bringing down the server, interrupting users and customers, and risking server reconfiguration problems.
SAN-What You Should Know
Business-critical data is a vital company asset and should be protected as such. Implementing the SAN architecture into an organization's existing computer infrastructure can guarantee the uninterrupted availability and reliability of this important data. The popular Fibre Channel fabric A Fibre Channel fabric (or Fibre Channel switched fabric, FC-SW) is a switched fabric of Fibre Channel devices enabled by a Fibre Channel switch. Fabrics are normally subdivided by Fibre Channel zoning. Each fabric has a name server and provides other services. interface often used in building a SAN provides fault-tolerant operations, protecting access to stored data at all times, even upon the failure of a server or other major network component.
Overall network operations are improved by the installation of even a basic SAN. Sites employing bandwidth-hungry applications, such as video, CAD/CAM CAD/CAM
in full computer-aided design/computer-aided manufacturing.
Integration of design and manufacturing into a system under direct control of digital computers. , or imaging find that the resulting increased bandwidth capabilities greatly enhance overall I/O (Input/Output) The transfer of data between the CPU and a peripheral device. Every transfer is an output from one device and an input to another. See PC input/output.
I/O - Input/Output and network performance. The Fibre-Channel interface provides improved response time on any network running high-end I/O applications such as databases or OLTP (OnLine Transaction Processing) See transaction processing and OLCP.
OLTP - On-Line Transaction Processing . Further improvement in overall network performance can be achieved through zoning and high-availability clusters. Though different from the NAS structure, SAN implementation allows scalable storage that is independent of any specific server or operating system operating system (OS)
Software that controls the operation of a computer, directs the input and output of data, keeps track of files, and controls the processing of computer programs. platform on the network.
Basically, the introduction of SAN architecture has brought about more cost-effective, high-availability storage for a wider variety of application environments. Thanks to the electrical isolation of SAN components provided by switches, the hot-pluggable nature of SAN resources allows much easier (and safer) scalability. The SAN dedicated network enables more efficient data management, backup and recovery of lost or corrupted data, and storage node configuration, while preserving ubiquitous data access.
NAS-What You Should Know
NAS storage devices are self-contained with their own embedded software Instructions that permanently reside in a ROM or flash memory chip. Embedded software may be immediately available to the CPU or, for faster execution, may be transferred to RAM first and then executed. , power supplies, and circuit boards, and so are easy and fast to install. Many can be installed by simply plugging them into an open LAN port without interrupting network service. Unix and Windows NT (Windows New Technology) A 32-bit operating system from Microsoft for Intel x86 CPUs. NT is the core technology in Windows 2000 and Windows XP (see Windows). Available in separate client and server versions, it includes built-in networking and preemptive multitasking. sites appreciate the almost automatic startup of NAS device insertion. Once initialized, the NAS appears on the network and to applications as another server (the embedded software has detected and configured the existing network), running immediately.
These simple machines have fewer components and software modules because they are optimized to perform a single function--high-performance file access and storage across the network--and are thus extremely reliable. The NAS devices can be monitored through a remote console A terminal or workstation in a remote location that is used to monitor and control a local computer. across the TCP/IP network, a serial console connection, or a GUI (Graphical User Interface) A graphics-based user interface that incorporates movable windows, icons and a mouse. The ability to resize application windows and change style and size of fonts are the significant advantages of a GUI vs. a character-based interface. using a Java-capable browser. And, an overall boost in system performance can be achieved by off-loading the data access and retrieval chores from the busy general-purpose network servers to the NAS. If the need arises, it is quick and easy to install additional NAS devices. They just "plug-in" as the first one did.
With few exceptions, most user applications find they suddenly have more storage available without ever noticing the addition of the Network Attached Storage file server. The NAS itself provides only file service. Applications continue to run on the local server that accesses the NAS using NDMP (Network Data Management Protocol) An open standard for backing up data in a heterogeneous environment. Developed by Network Appliance and IntelliGuard Software, NDMP uses a common data format which is written to and read from drivers for the specific disk and (Network Data Management Protocol). NDMP addresses the high overhead and security issues that plagued CIFS (Common Internet File System) The file sharing protocol used in Windows. It evolved out of the SMB (Server Message Block) protocol in DOS, which is why the terms CIFS/SMB and SMB/CIFS are sometimes seen. The word "Internet" in the CIFS name has little relevance. and NFS (Network File System) The file sharing protocol in a Unix network. This de facto Unix standard, which is widely known as a "distributed file system," was developed by Sun. See file sharing protocol and WebNFS.
NFS - Network File System file accesses.
Like the SAN, NAS also enhances the network backup process. Network attached backup processes see the NAS as if it were another local disk. The Unit-type "dump" command can be used to "dump" a whole or partial file system image to tape media or an optical disk device. The NDMP option works in conjunction with Legato's NetWorker or Veritas' NetBackup enterprise-wide backup solution to direct the files on the NAS device to a locally attached Refers to disks, printers and other peripheral devices that are connected directly to a computer via USB or FireWire. Such devices may be designed for desktop use or portability. For example, a locally-attached, stationary hard drive may weigh three to five pounds, while one made for backup system Noun 1. backup system - a computer system for making backups
ADP system, ADPS, automatic data processing system, computer system, computing system - a system of one or more computers and associated software with common storage controlled tape or similar device.
The Merging Of SAN/NAS Storage Options
As SAN and NAS each have drawbacks that counter their many benefits, creative IT and storage administrators are pulling from both storage techniques in order to implement a storage environment that merges the best of both worlds. The market is pushing for the merging of the SAN and NAS options into something we can call Enterprise Storage Networking.
SANs promise to eliminate the many independent islands of server storage prevalent within most large corporations today and consolidate them into one, centralized cen·tral·ize
v. cen·tral·ized, cen·tral·iz·ing, cen·tral·iz·es
1. To draw into or toward a center; consolidate.
2. heterogeneous storage subsystem. NAS, on the other hand, has the field-proven ability to seamlessly connect storage and share data over a heterogeneous environment Using hardware and system software from different vendors. Organizations often use computers, operating systems and databases from a variety of vendors. Contrast with homogeneous environment. . However, its reliability in this area is tempered by its underlying shortcomings A shortcoming is a character flaw.
Shortcomings may also be:
The logical solution to these dilemmas is the merging of the two storage architectures into one storage networking subsystem. This Enterprise Storage Network employs NAS to provide file and data (under specified conditions) sharing over standard network interfaces (e.g., Ethernet or Gigabit Ethernet An Ethernet standard that transmits at 1 Gbps. Used mostly to connect high-end workstations and servers as well as for network backbones, Gigabit Ethernet transmits full duplex from point to point using switches and half duplex in a shared environment (CSMA/CD) using a hub. ). It utilizes Fibre Channel SAN to provide dedicated high-speed storage access with greater levels of redundancy to database applications and network storage devices (such as a RAID or an optical library).
This NAS/SAN topology combines the power of NAS (easy, reliable sharing and scaling of storage over the standard network regardless of operating system or server types) and the speed and availability of SAN (access to multiple storage devices over a fast and fault-resilient dedicated Fibre Channel) to formulate a multifaceted data access and handling infrastructure that is capable of meeting all of the enterprise's storage requirements.
By combining SAN and NAS storage architectures, many of the storage application problems facing IT administrators today can be solved. SANs provide for the mixing and matching of storage devices and dynamic reassignment of storage space and units to multiple servers. NAS is well suited for adding capacity to file servers without interrupting network operations. In a merged environment, NAS serves as an "intelligent gateway" to the SAN, enabling end-users speedy and reliable access to their data.
NAS and SAN combine to provide quick storage and capacity scaling, storage consolidation, and LAN-free backup A LAN-free backup is a backup of server data to a shared, central storage device without sending the data over the local area network (LAN). It is usually achieved by using a storage area network (SAN). with simplified storage management. By combining the single network-centric administration and file sharing Copying files from one computer to another. See peer-to-peer network, file sharing protocol and file and printer sharing. of NAS with the performance and data-centric SAN, storage administrators can meet the most demanding storage application requirements.
Terry Grulke is storage product manager at StorNet, Inc. (Englewood, CO).