iSCSI deployment in business IP storage network

Computer Technology Review, May, 2004 by Robert Lusinsky, Mark Woithe

According to industry experts, Internet Small Computer Systems Interface (iSCSI) represents a major technology that converges the best of traditional storage and network infrastructures. IP-based Storage Area Networks (IP SANs) are often based on the iSCSI protocol, a standard method of encapsulating SCSI commands into TCP/IP packets and transporting them over standard network infrastructures. IDC predicts the total market for iSCSI-based disk arrays will grow from $216 million in 2003 to $4.9 billion in 2007 (118% CAGR). One reason for this explosive growth is that iSCSI SANs provide more flexibility than direct-attached storage (DAS) at a lower infrastructure cost than Fibre Channel SANs, by enabling enterprise applications such as e-mail, databases, and remote disk/tape backup to move data over TCP/IP networks. Since IT personnel are already familiar with Ethernet networking technology, the total cost of ownership (TCO) for an iSCSI SAN is dramatically reduced.

Managing the storage networking requirements for an estimated 6-8 million small to mid-size businesses (SMB) can be quite a challenge for IT professionals as they prioritize spending in key areas such as data protection, network security, storage capacity and management. In addition, retention of company data is being driven by government regulations such as SEC Rule 17a-4, HIPAA, 21CFR Part 11, Sarbanes-Oxley and the Patriot Act. Given these requirements, IT professionals have three possible solutions for storage expansion and management:

DAS: Direct Attached Storage

NAS: file-based Network Attached Storage

SAN: block-based Storage Area Network (SAN)

DAS is inflexible because expansion and management of storage capacity can be very difficult. Although networked storage (NAS/SAN) provides much needed relief, NAS does not efficiently handle I/O-intensive applications such as databases, leading to performance degradation. Finally, Fibre Channel SANs may be cost prohibitive for many SMBs to install and manage.

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The best solution is an iSCSI SAN. iSCSI SANs are based on industry standards that can leverage the existing IP infrastructure and allow the movement of data over a network between storage subsystems and application servers. The benefits of an iSCSI SAN can be realized almost immediately: lower cost, reduced complexity, leveraged IT investment, easy storage expansion, performance advantages and ease of deployment. Collectively, these benefits resolve key IT challenges for SMBs: interoperability and management.

Interoperability

The common IT complaint today about SAN is interoperability. Fibre Channel (FC) devices, which are commonly used to create SANs, often are incompatible with each other. Despite the great strides FC vendors have taken to address the issue, interoperability problems continue to persist and require most FC vendors to maintain large compatibility lists.

Interoperability issues between iSCSI devices today are minimal and are expected to disappear altogether. The reasons iSCSI has very few interoperability issues can be traced to several factors.

First and most important, iSCSI utilizes the Transmission Control Protocol/Internet Protocol (TCP/IP) for transporting iSCSI packets between network connections and utilizes SCSI as the storage protocol. TCP/IP has existed for over 20 years and is now the de facto standard network protocol for most private and public networks. TCP/IP has been standardized and refined such that interoperability between different devices utilizing TCP/IP is rarely an issue. SCSI technology, in like fashion, has existed for decades and is a well-understood standard, especially for storage devices. The end result is that TCP/IP and SCSI are proven technologies and serve as excellent transport protocol and storage protocol for iSCSI.

Second, the iSCSI specification continues to be vetted through many different mechanisms. The specification is only a starting point and ensuring that all companies adopt a single, compliant interpretation of the specification is important, especially for business IT professionals. The iSCSI industry has cooperated to ensure interoperability through a consistent interpretation of the iSCSI specification. For example, the University of New Hampshire Interoperability Labs (UNH-IOL) hosts iSCSI Plugfests that allow companies to test interoperability with the products from other vendors. Also, UNH-IOL has a standard iSCSI compliance test that can be executed against iSCSI implementations to verify compliance. This interoperability test, in addition to Microsoft's Windows Hardware Quality Lab (WHQL) compliance test, ensures that the industry is moving to a single interpretation of the iSCSI specification and avoiding the ambiguities that have plagued other storage network solutions.

Lastly, many large vendors have stepped up to the plate early to provide iSCSI solutions. Most notably, Microsoft has played a large role in promoting iSCSI through the introduction of its iSCSI Software Initiator. Microsoft's iSCSI software initiator may be slower and increase CPU utilization when compared to hardware accelerators, but the popularity of the software initiator has surged and has helped to resolve interoperability issues by eliminating another variable in interoperability.