storage industry has seen the emergence of too many
standards, some of which are relatively immature. An
enterprise should study the pitfalls of each and make
a decision to go with the chosen one. by Soutiman Das
network storage and the concepts of NAS and SAN have
been around for quite a while, the storage industry
is still plagued with the lack of a definite standard.
Even before existing standards like Fiber Channel (FC)
and InfiniBand gained worldwide acceptance, newer ones
like iSCSI, CIM (Common Information Model), and Bluefin
are in various stages of acceptance. And interoperability
between products which support different standards in
most cases is questionable.
Simon Harvey, Managing Director, Asia Pacific, Storage
Solutions Group, Quantum Corporation, says, "The
word 'interoperability' means different things to different
audiences and yet remains a top concern among end users.
media often refers to the problem as 'a lack of standards,'
but it is really an issue of getting the vendors to
agree on the standards that already exist."
Whether we appreciate it or not, multi-vendor storage
is a reality and will continue to be a part of an enterprises
network. And this is the reason why organizations will
respect and stick to network management tools and applications
that work in heterogeneous environments.
Bithin Talukdar, Market Development & Alliances,
Software Global Business Unit, HP, says, "Vendors
who continue to try to lock in companies with a proprietary
approach will find themselves locked out by customers."
SAN and the Fiber Channel
An FC interface is typical of a SAN. V.K. Ramani, President-IT,
UTI Bank explains, "A SAN is an architecture of
a network separate from the LAN. It is a separate computer
network typically based on the 'fabric' of fiber channel,
switches, and hubs that connect storage devices to a
heterogeneous set of servers on many-to-many basis."
SANs can provide increased performance, scalability,
data protection, resiliency, availability, and manageability.
Performance is improved because servers talk directly
to the storage and other servers on a separate 1 Gbps
network. It does not have to contend with normal LAN
traffic like Service Advertise Protocols (SAPs) and
Acknowledgements (ACKs). The LAN also does not have
to deal with storage traffic like unattended backup
The FC standard addresses the need for very fast transfers
of large amounts of information and can scale up to
1 Gbps. The fast technology can be converted for LANs
by adding a switch specified in the FC standard which
handles multipoint addressing. FC gives users one port
that supports both channel and network interfaces, unburdening
the computers from a large number of I/O ports, and
provides control and complete error checking over the
link. In storage terms, the switches (and other hardware)
connecting the servers to the storage devices in a SAN,
are collectively called the Fabric.
Instead of sending data in parallel across the backplane
bus, InfiniBand specifies a serial bus. The serial bus
can carry multiple channels of data at the same time
in a multiplexing signal. InfiniBand also supports multiple
memory areas, each of which can be addressed by both
processors and storage devices.
It offers throughput up to 2.5 Gbps and support for
up to 64,000 addressable devices. The architecture promises
increased reliability, better sharing of data between
clustered processors, and built-in security.
Unlike the present I/O subsystem in a computer, InfiniBand
seems like a full-fledged network. The InfiniBand Trade
Organization describes the new bus as an I/O network
and views the bus itself as a switch since control information
will determine the route a given message follows in
getting to its destination address.
Internet Small Computer Systems Interface (iSCSI) is
an IP-based storage networking standard for linking
data storage facilities, developed by the Internet Engineering
Task Force (IETF). By carrying SCSI commands over IP
networks, iSCSI can manage storage over long distances.
Due to the ubiquity of IP networks, iSCSI can be used
to transmit data over LANs, WANs, and the Internet.
It can also enable location-independent data storage
Common Information Model (CIM) is an encoding specification
based on XML, and a transport mechanism based on HTTP.
CIM enables Internet-based system-level management.
It's basically an object-oriented information model
that provides a conceptual view of the physical and
logical system management entities. It is implementation-independent
and allows the interchange of management data in multi-platform
distributed application environments.
It is based on CIM and is an object-oriented messaging
interface that links distributed management applications
(clients) with device management support (agents). The
agents can be embedded in the storage resource or run
on a proxy server.
Bluefin will enable storage integrators deliver consolidated
management solutions by providing a common interface
that allows reliable and secure multi-vendor interoperability
in a SAN environment.
NAS and SAN differentiation blur
The boundary between NAS and SAN may soon blur. It doesn't
matter whether data travels over a FC on a separate
network, or simply attached to the network, or perhaps
a mixture of both. Enterprises are primarily interested
in availability, security, reliability, and ease of
To sum it well, UTI Bank's V.K. Ramani says, "There
may be many emerging technologies that promise better
features and manageability, but it is not necessary
to move to it just because it's there. Storage is still
seen as one of the less glamorous aspects of IT management
and it's difficult to generate adequate excitement for
claiming enhanced IT budgets. However, the IT manager
should be in a position to put forward a business case
in view of its importance for data management, which
essentially is the key to availability of information
that cannot be ignored by the organization."
Soutiman Das Gupta can be reached at