|Introduction to NAS - Network Attached Storage|
|The terms "NAS" and "SAN" often get confused|
NAS vs. Traditional File ServersProponents of NAS claim that NAS technology provides these advantages over traditional file servers:
NAS products improve on traditional file servers generally through the principle of simplification. By stripping out all of the unnecessary capabilities of a general purpose server -- applications, services or daemons, and hardware peripherals -- a NAS device becomes less prone to system "crashes" and security attacks. When a problem does occur, a NAS system can be diagnosed and rebooted much faster due to its lower level of complexity.
NAS products also generally hide the operating system personality of the device. Whereas Windows, UNIX and NetWare file servers each demand specific protocol support on the client side, NAS systems strive for greater operating system independence of clients.
Opponents of NAS emphasize that traditional file servers have a proven record of success compared to this new breed of "upstart" NAS systems. High-end file systems also contain more processing power than a NAS device, giving servers a performance edge (in terms of transactions or I/O per second rates) over NAS.
NAS vs. SAN
At a high level, Storage Area Networks (SANs) serve the same purpose as a NAS system. A SAN supplies data storage capability to other network devices. Traditional SANs differed from traditional NAS in several ways. Specifically, SANs often utilized Fibre Channel rather than Ethernet, and a SAN often incorporated multiple network devices or "endpoints" on a self-contained or "private" LAN, whereas NAS relied on individual devices connected directly to the existing public LAN. The traditional NAS system is a simpler network storage solution, effectively a subset of a full SAN implementation.
The distinction between NAS and SAN has grown fuzzy in recent times, as technology companies continue to invent and market new network storage products. Today's SANs sometimes use Ethernet, NAS systems sometimes use Fibre Channel, and NAS systems sometimes incorporate private networks with multiple endpoints. The primary differentiator between NAS and SAN products now boils down to the choice of network protocol. SAN systems transfer data over the network in the form of disk blocks (fixed-sized file chunks, using low-level storage protocols like SCSI) whereas NAS systems operate at a higher level with the file itself.
The new breed of NAS networking products has succeeded in providing a reasonable alternative to traditional file servers in client/server networks. Entry-level NAS products containing 20-50 gigabytes of storage can be purchased for $500 (USD) or less, whereas mid-range and high-end NAS systems can run in the tens of thousands of dollars. Besides cost, a NAS promises reliable operation and easy management. Look for the Network Attached Storage technology to keep evolving as the field matures over the next several years.
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