and managing data is an important business need for an enterprise.
P. P Subramanian shares his thoughts on the various storage
alternatives enterprises have
to the National Storage Industry Consortium, the amount of
data stored on the world’s network is now 1,000 Petabytes
ultimate goal for IT organizations is to view and manage all
its storage and share data across all types of platforms.
But to access the same data on the same disk is an elusive
and managing data in an enterprise is not just a technology
need but an important business need as well. It's imperative
to keep abreast of storage mechanisms and techniques to deal
with the problem of managing storage. There is a deluge of
technologies to choose from. And a whole bunch of new technical
jargon that goes along with it. This jargon doesn't make it
easier to understand new technologies.
Out of the many storage technologies that have emerged, let
me throw light on the confusion created by SAN (Storage Area
Network) and NAS (Network Attached Storage).
SAN is not a new technology. It is one of the two storage
innovations that have emerged in response to the ever-increasing
demand for data storage (the other being NAS). SAN and the
less costly NAS capitalize on low storage costs and fast network
speeds. They rely on high-speed networks to build fast and
highly available systems to store and retrieve large amounts
The large demand for storage arises from the increased use
of Internet and Intranets, applications like data warehousing
and video, and the potential of e-commerce. According to the
San Diego-based National Storage Industry Consortium, the
amount of data stored on the world's network is now 1,000
Petabytes (or 1 million Terabytes).
Just like variety of mobile technology options create confusion
among mobile phone users regarding which technology is the
right one for them, people readily interchange SAN and NAS,
creating confusion and slowing adoption. The confusion partly
arises because the two technologies share many similar features.
Both are used for scaling storage capacity and performance,
and can be expanded step-by-step as the need for greater storage
arises. Both topologies enable companies to purchase storage
separately from servers, which means organizations can tailor
their purchases to their needs. Both are capable of making
data available to a variety of users across multiple OSs.
Both are highly available. And a thing to note is that the
availability of stored data isn't necessarily dependent on
the availability of an organization's multi-purpose server.
Both can reduce long-term operating costs by offering centralized
storage management. Organizations don't need separate storage
for data generated by Unix systems, NT systems, Novell servers,
and other proprietary networks.
But there are significant technical and cost differences.
The key element of a NAS system is a dedicated 'thin' server
that manages the storage and flow of data across the network
between clients and an array of disks. NAS relies on standard
LAN/WAN connections. And since it supports multiple communications
protocols, it can store data from a variety of heterogeneous
A SAN on the other hand, is a dedicated, high-bandwidth, fiber-channel
network that connects storage disks to one or more servers
and incorporates SCSI, fiber-channel or ESCON (Enterprise
Systems CONnection A mainframe technology) links. SANs are
typically more complex and difficult to operate in a heterogeneous
environment, but they are highly reliable and offer greater
speed and better integrity of data.
The two technologies are targeted at different applications
and environments. NAS is emerging as a popular choice for
organizations of all sizes that want rapid access to files
across heterogeneous servers. SANs are more widely deployed
in highly specialized applications like multimedia and video,
where the volume of data storage is very large. It can also
be used in business-critical environments, where redundant
and highly available storage is crucial. SANs are faster than
NAS systems are generally less costly than SANs. NAS systems
are used where budgets call for systems in the sub-$10,000
range. SAN installations, including disks and fiber-channel
networks, start at $25,000.
Both technologies are expected to gain a wide following. Market
research firm IDC estimates that SANs, including mainframe
ESCON and Digital VAX VMS-type SAN systems (Compaq proprietary),
will generate $11.4 billion in revenue in 2002, up from about
$3 billion in 1998. Dataquest estimates that the market for
NAS appliances, as the thin servers are called, will reach
$10.5 billion in 2002, up from $900 million in 1998.
Some businesses view NAS as a stepping-stone to SANs, which
are more difficult to operate in a heterogeneous environment.
Yet while SANs are faster than NAS systems, NAS is not exactly
Pre-assessment for better understanding
Ultimately, the goal for IT organizations is to view and manage
all its storage and share data across all types of platforms.
But enabling multiple users to access the same data on the
same disk is an elusive goal. This is because NAS uses file-system
protocols like NFS (Network File System) for Unix and CIFS
(Common Internet File System) for NT to access and share data
across systems. In a SAN, the process of sharing data across
multiple OSs is a more complex proposition. Whichever technology
is used, a careful assessment of the pros and cons of both
SANs provide high-speed access via fiber-channel links to
large stores of data like data used by digital video and audio
applications. They are designed for applications where data
integrity, availability, and reliability are a must. Mirrored
sites, for backup and recovery, can be located up to 10 Kms
apart. SANs use reliable SCSI-type connections, not network
protocols such as NFS, FTP, HTTP and CIFS.
The high-speed features come at a steep price. SANs cost more,
with installations starting at $25,000 and rising steeply,
depending on the size and complexity of the solution required.
SANs are also usually limited to LANs due to the cost of running
fiber-channel links over longer distances.
Data sharing in a SAN is a difficult proposition which requires
that each OS has knowledge of the others' data and metadata
formats. SAN installation is typically more complex than NAS
installation and may require custom configuration.
On the other hand, NAS is a simple and elegant solution for
fast, wide-ranging access to data storage. It requires few
or no changes to many organizations' existing networks. NAS
enables access to data from multiple servers with different
OSs. It's relatively inexpensive you can get disks and a thin
server for $10,000. The thin-server technology can be distributed
across a large network, but centrally managed. NAS systems
can work with lower-speed connections.
The disadvantages of NAS include a lack of built-in security.
Organizations must use firewalls to tackle this. NAS isn't
well tuned for storing enormous amounts of data because of
the load that it puts on the network. Disaster recovery or
tolerance requires a customized solution.
It's a good idea to ask your peers to help you decide which
products will best suit your needs. Chances are that someone
will have tried and tested it before you. Remember the old
maxim: don't re-invent the wheel
P. P Subramanian is Country Manager (India),
Hitachi Data Systems and can be reached at firstname.lastname@example.org