The Convergence of NAS and SAN

The demand for storage capacity is surging leaps and bounds. This demand is

further fueled by the growth of the Internet and a pressing need for online

access to critical data. The ability to access data in real time has become a

mission-critical capability for every enterprise. But at the same time,

cash-strapped enterprises are also bound to improve data management and reduce

the total cost of ownership. The storage industry, sensing these needs, is

responding with innovative storage networking technology that will add value to

enterprise storage network architecture.

These emerging storage technologies will help enterprises in creating shared

storage pools that can scale seamlessly. Enterprises will also be able to

significantly reduce backup times by leveraging online archives and new types of

secondary storage media. Last but not the least, these companies will have the

power of better manageability of data because they would be able to control the

database from a central location. These things will help the enterprise achieve

the much sought-after TCO in their storage architecture.

All these benefits make a much-required case for revolution in data storage.

network-attached storage and storage area networks have proven value to an

enterprise, but their differences can make data administration unnecessarily

complex and costly. Storage networking, whether NAS or SAN, has become essential

to mission-critical IT environments. These are actually two of the most dominant

trends in data storage. According to Gartner, a research agency, end-user

expenditures on storage networking solutions will exceed $65 bn in 2003. This

situation will compel the storage managers in enterprises to think of how they

can get the maximum return from a major investment in storage network

architecture? This brings us to the much-hyped debate about the relative value

of NAS and SAN technologies.

Network-attached storage



NAS filers are special-purpose file servers, i.e., "appliances"

that attach to a LAN and deliver files to client systems or even other servers,

which act as clients through the LAN. An important NAS attribute is that the

client system running different operating systems such as Windows and Unix can

share NAS files. A NAS filer lets clients share files but that storage is not

shared with other servers. Most of the NAS devices support the Common Internet

File System and Network File System associated with, respectively, Windows and

Unix operating systems. It also supports file systems of Macintosh, Novell, and

other such OSs. So we can say that a NAS is essentially a plug-and-play storage

solution based on industry standards and attached to a LAN/MAN/WAN. Its inherent

design eliminates server I/O bottlenecks on heterogeneous networks by providing

cost-effective storage and file sharing.

Storage area network



SAN storage connects to multiple servers through a separate storage area

network, and via LAN. In this architecture servers access the files using basic

block I/O commands making it look like as if the storage was part of the server.

SAN does not usually offer file sharing, it offers storage sharing to servers.

The storage sharing can be physical or partitioned logical storage. Also, the

SAN provides a high-speed data path between server and storage independent of

the LAN. Thus SAN can be described as a vision for an open, scalable, fibre

channel architecture that interconnects storage systems, backup devices and

servers. It absorbs LAN traffic to improve network performance.

Many enterprises can take advantage of the strengths of both SAN and NAS

technology. The desire to more efficiently manage network storage and use the

different storage technologies is the strongest cause for the convergence of

SANs and NAS to create a single enterprise-wide storage solution.

The next step: NAS-SAN fusion



It’s clear that SAN and NAS architectures aren’t necessarily competing

technologies but are complementary solutions that can be implemented together to

improve manageability and efficiency of backup and storage-related tasks along

with the overall system performance. The fusion of SAN and NAS stands to provide

enterprises with substantial benefits and a much broader range of options.

What will drive this convergence is another important thing to be considered

seriously. Below are some issues that affect NAS and SANs:

n  NAS is

not as scalable as SAN. It can only be readily scaled by adding capacity up to

multiple terabytes or by adding multiple NAS appliances to the network. On the

other hand, a fully functional fibre channel SAN is also not available because

interoperability standards still remain unclear. Meanwhile, gigabit Ethernet

SANs have been introduced to provide a more standardized approach to SAN

architecture. But the industry still faces the challenges of incorporating SANs

into a coherent strategy that leverages the huge infrastructure based on

networking technology. These are the causes that will drive the convergence of

NAS and SANs.



n  Those of you
who are committed to both NAS and SAN recognize that some of the powerful

features you want in your storage network are available in NAS and some of them

are in SAN. Therefore, the best method to get a best of NAS and equally good SAN

is to converge. In these tough times the cash strapped companies now

predominantly want minimum five-year return on their technology investments.

They want to leverage their existing infrastructure investments, including

people, application software, networking infrastructure and other hardware.

Convergence of the two will give them a longer life for their investment in

storage. Merger of NAS and SAN implementations will reinforce each other thus

making the business continuity possible for the companies even when they are

changing their whoel infrastructure.



n  With this convergence, a powerful and efficient storage

architecture can be created. For example, a NAS server with a SAN backend will

provide you an easily expandable storage capacity solution, while the SAN

infrastructure, using Fibre Channel I/O connections, will provide lightning-fast

data transfer and a highly reliable and scalable storage subsystem.



n  A
significant technology trend that will drive NAS-SAN fusion is the rapid rise in

networking speed. Network speeds are now surpassing storage speeds, blurring the

lines between NAS and SANs from the standpoint of the technology. Customers will

soon begin to focus more on the value proposition of storage networks and worry

less about the much-coveted Gigabit Ethernet versus Fibre Channel architecture

debate.



n  Finally,
Direct Access File System (DAFS), a protocol based on virtual interface (VI)

standards will also drive this fusion. It abolishes storage I/O latencies by

using Direct Memory Access (DMA) between servers and storage memory

architectures. It is primarily aimed at the storage network environment and is

medium agnostic.

What it should provide



The converged NAS/SAN product a "two dialect device" or 2DD for

short should do the following:

n  It should

facilitate high-speed block I/O transfers between servers and storage on a

point-to-point basis



n  It must
provide high-speed data path for bulk I/O transfers, such as for

storage-to-storage backup, and



n  It should
also allow the consolidation of server storage.



n  It should
also be capable of delivering files over a LAN (or wide area network, such as

the Internet like a typical NAS device does) and



n  It should
allow file sharing among server platforms running diverse OS’ (another NAS

quality).

Storage networking technology, built around this convergence, will have both

NAS and SAN technologies. On one side are storage technologies and storage

protocols to manage disk systems. On the other side are network protocols for

delivering the data from storage to the outside world, including database

servers. These network protocols also provide high-speed access to a common

automated tape library.

NAS and SANs are complementary technologies. They are converging today under

the pressure powerful technology trends. OSN is the ultimate force that drives

the convergence and permits standards-based, best-of-breed solutions. HP, the

first among few companies proposing this NAS-SAN fusion, calls this fusion a ‘Universal

Networked Storage’. The company is offering users the ability to add a NAS

capability to any of the existing SAN blueprint configurations. The latest NAS

solution from the company is available in SAN-attach configuration, and is

compatible with the OpenView Storage Area Manager suite.

The author is marketing manager (NSSO) at HP India. He can be contacted at mail@dqindia.com