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