Traditionally, IT departments turned to direct attached storage methods such as stand alone hard disks, RAID arrays, tape and optical media, which connected a single storage host to a single resource, such as a server or a workstation through an I/O bus. The variety of methods presented an equally wide range of concerns, including cost of ownership, scalability and manageability issues.

So much for tradition. Storage area networks (SAN) and network attached storage (NAS) are now deployed in many businesses. These technologies let you share storage resources among a much larger number of processing systems and users, and can improve efficiency and simplify management.

Networked storage technologies also let you access data more quickly, since you can share the data across multiple platforms regardless of the device or operating system you're using.

SAN and NAS defined:

Besides the fact that SAN is NAS spelled backward, there are fundamental differences between the technologies and their mirror-image acronyms. 

A NAS solution is a means by which you may attach a storage subsystem to a LAN network making the data contained on it available across the Ethernet network. This architecture allows various hosts to access a centralized “data pool” without having to first interface with several different hosts on which that data would otherwise reside. Therefore NAS optimizes media usage (Disk, Tape, Optical) and centralizes management raising the over all ROI of your data management systems. Due to the fact that the data is transferred across an existing LAN the initial investment to implement a storage virtualization solution such as this would be kept to a minimum. However, saturation of the network may also become a concern and it may become necessary to upgrade the existing LAN environment, or eventually migrate off of the LAN and move to a SAN solution instead.

SANs can solve connectivity problems among many storage devices and servers. A SAN also offers new approaches to storage, such as disk and tape pooling, heterogeneous data sharing, and off-the-network/serverless backup and restoring. This secondary network relieves the main network of massive data transfer loads because backup traffic occurs between storage devices inside the SAN.

The benefits of SAN/NAS:

Networked storage provides one big boon to the enterprise: Considerable IT staffing cost reduction. Storage management consumes about 55 percent of the overall storage budget in a distributed environment. By comparison, SANs bring that figure down to between 15 and 20 percent of the overall budget. And NAS devices are even easier to manage because they simply plug in to the network and are focused on specific file-serving needs. GUI-based management software further eases the administration of these storage systems.

Breaking down the benefits:


Easy to add
  You can add NAS appliances--which are particularly suited to any application with intense read/write activity--to the network within minutes, without bringing your LAN down. 
Take the heat off your network server
  NAS devices increase storage-on-the-fly capabilities, which you can use to redirect network traffic and reduce the need to add more network nodes. Enterprise managers can offload high-bandwidth, file-serving tasks from the network server, which in turn reduces latency, which might interfere with critical business tasks such as application handling and email. NAS flexibility lets you add storage wherever you need it, even to remote locations. Finally, with NAS, you can perform backups without affecting network server performance.
Facilitates data sharing
  The modern network is a heterogeneous environment, and NAS lets you connect to multiple operating systems and share data among disparate clients and servers. NAS supports both the Network File System (NFS) protocol for Unix and the Common Internet File System (CIFS) for Microsoft in order to facilitate this cross-platform data sharing.


Consolidates information
  The biggest single benefit of a SAN is that it lets you consolidate a huge amount of information into a centralized storage network. The SAN connects all the storage and offloads the network traffic associated with storage access onto the separate network. This translates into lower latency and more efficient resource utilization.
Faster data retrieval
  By utilizing Fiber Channel technology, SAN provides true 100-MB/s data speeds. Compare these numbers to today's SCSI technology, which provides mainly speeds of 40 or 80 MB/s, and you have significantly faster data speeds. (However, newer SCSI technology is being developed that promises to bring SCSI speeds to near parity, although current technology does not allow SCSI networking) SANs can also support a nearly limitless number of devices if your company is willing to invest in the infrastructure (servers, multiplexers, bridges, and storage devices).
Easier backup and recovery
  SANs also make it easier for companies to make backups and do disaster recovery. Data can be mirrored to a remote location for seamless disaster recovery or backed up quickly to another location without affecting network speeds. In a SAN, you can save gigabytes of data in a matter of hours. In addition, SANs provide a variety of network-enabled techniques--such as alternate pathing, clustering, failover, mirroring, and replication--that protect against data loss and improve the availability of information.
Exceptional scalability
  A SAN, with its inherent and almost unlimited scalability, is a particularly good choice for networks that grow quickly or have sporadic needs for higher storage capacity levels. With repartitioning and management tools, network administrators can reallocate storage space from one server to another by simply repartitioning the SAN. Repartitioning assigns storage space to a network server instead of directly connecting storage space to a network server.
Access Time
  Particularly in the SAN environment, getting information quickly is critical. NAS devices serve pages and are noted for superior latency levels. SANs serve blocks of information, rather than individual pages.
  As SANs get larger and more complex, managing all the components becomes a greater challenge. Choosing the right management software is critical. A solid solution will allow SAN managers to control the entire storage network from a single interface and to change the parameters of the network to address changing storage needs.
Language Support
  When used for Internet-related purposes, support for different languages and character sets is vital. Users spread across a global enterprise, for example, may access information and use programs in many different languages.

The Bottom Line

Whether you're evaluating, designing, building, or buying a SAN or NAS solution, start simple and build to a more complex environment as needed.

Storage Standards

The Storage Networking Industry Association, for example, is working to drive a variety of standards. The group's host bus adapter (HBA) API standard will address some of the interoperability issues inherent in SAN technology for uniform functionality for HBAs.

The Future of Storage

The future of network storage technologies seems bright, especially with many companies seeking better ways to manage their storage infrastructures. Storage vendors are working to create more sophisticated software applications to provide single-console SAN management within a heterogeneous environment. In addition, the future promises a number of new standards that will increase interoperability and usability issues with SANs.

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