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Issue of December 2002 
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Storage Management
The standard way to storage

The 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 Gupta

Although 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.

The 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 enterprise’s 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 and storage.

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 and retrieval.

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 management.

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

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