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iSCSI deployment in business IP storage network.

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.


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.


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.


Why should IT professionals consider an iSCSI SAN? The overwhelming reasons are consolidation, scalability and manageability for a much lower price than the existing Fibre Channel SAN solutions today. Additionally, iSCSI solutions dramatically reduce the learning curve for deploying an IP SAN since iSCSI leverages existing and well-understood storage and networking technologies, which further reduces TCO.

Migration from direct attached storage to an iSCSI SAN is relatively simple since iSCSI leverages existing network and storage technologies. DAS compatibility with iSCSI is often seamless since iSCSI devices appear as locally attached storage devices. This means that existing applications and utilities used to manipulate DAS storage devices will normally work with iSCSI devices without any changes. Furthermore, iSCSI performance is usually equivalent to the performance of most DAS devices. The leveraging of existing storage network technologies lowers cost by reusing existing knowledge, thereby reducing the learning curve for an IP SAN without sacrificing performance.

Management of iSCSI storage is also relatively simple. Industry surveys regarding storage solutions have estimated that only 50%-70% of a business' storage is efficiently utilized. The remaining storage typically remains unused and non-useable, resulting in lost money and higher maintenance and backup costs. iSCSI resolves this issue by allowing storage to be placed on the network. Once on the network, the storage can be consolidated and managed more or less as a common storage pool. This allows for the easy provisioning and management, and results in better utilization of the available storage resources.

Backups also become easier. Since the storage is on the network, there are typically fewer servers required to perform backups. With DAS, a separate tape drive or backup agent was commonly installed in each server, driving up acquisition and monitoring costs. With storage on the network, only a single backup server with a single tape drive can serve the needs for an SMB. This reduces the cost of hardware while simultaneously reducing the cost of IT operations.

In addition to leveraging well-understood technologies, iSCSI has benefited from other technologies that might be a bit obscure or completely new. One lesser-known technology that iSCSI benefits from is Internet Storage Name Service (iSNS). iSNS servers act as a bridge between servers and storage that allow iSCSI initiators to identify and connect to iSCSI targets. iSNS allows initiators to dynamically discover and connect to iSCSI storage devices with very little information from the iSCSI initiator. iSNS will be important for large organizations deploying iSCSI SANs in order to automate iSCSI target device discovery. A new technology that is benefiting iSCSI is the iSCSI Management API (IMA). The Storage Networking Industry Association (SNIA) is spear-heading the development of the IMA, which is a management interface for iSCSI adapters that helps refine management even further through a common API that enterprise framework and storage management applications can access. Technologies such as iSNS and IMA will help accelerate the adoption of iSCSI.

Business Solutions

The business solutions afforded by iSCSI are numerous. Businesses are always seeking ways to lower costs and iSCSI complements this requirement with simplicity and ease of implementation. The net result is business solutions with lower costs coupled with cheaper deployments and easier maintenance.

For example, because iSCSI interoperability is high and iSCSI is operating system agnostic, having an iSCSI target based on Linux while the iSCSI initiator is running on Windows is not an issue. This allows for common applications that only run on Windows to transparently access storage hosted on Linux machines. Case in point, Windows NAS server front-ends can be created that utilize Linux iSCSI SANs for the backend storage. Additionally, since the backend storage for the NAS is on the network in the form of a SAN, scaling and provisioning the storage for NAS usage is simplified. The users of the NAS storage are provided in easy-to-use shared file-level storage, while IT is provided an easy method of managing the storage for the NAS front-end server.

iSCSI also excels at remote copies. There are iSCSI solutions on the market today that allow two iSCSI storage subsystems to be in two separate buildings that basically mirror each other. This is easy with iSCSI since iSCSI is based on TCP/IP, so there are no real distance limitations for iSCSI. Placing the two iSCSI mirrors in different buildings helps protect the data by providing the benefits of a remote copy. iSCSI essentially relegates tape to archiving purposes for recovery and regulatory functions, as opposed to the traditional primary responsibility of disaster recovery.

iSCSI has also excelled as the backend storage for backup and archiving solutions. As an example, Disk-to-Disk-to-Tape (D2D2T) solutions can utilize the easy provisioning functions of iSCSI to optimally use storage for data disk backup to an intermediate disk. The tape can then perform the backup from the intermediate disk storage. Snapshots also are a big cost reduction mechanism since users can regularly restore their own files in minutes rather than relying on IT to restore files, which frequently takes hours. iSCSI provides an easy mechanism to manage the storage for the snapshots since the snapshot storage requirements often change from month to month.


iSCSI SANs reduce capital and operating storage expenses of DAS by networking and consolidating pools of storage. Xiran improves iSCSI SAN solutions further by providing the following benefits:

* Advanced iSCSI technology with proven interoperability

* Full offloading of TCP/IP and iSCSI processing

* Easy manageability through a Web browser interface

* An easily scalable solution to match today's performance requirements

Xiran's iSCSI target storage adapters utilize Xiran's patented DirectPath Engine (DPE) to efficiently move data from the network to the storage subsystem. The full TCP/IP and iSCSI offloading allow Xiran iSCSI targets to move more data for a lower cost than competing products, reducing TCO. In addition to simplifying the deployment of an iSCSI SAN, Xiran provides iSCSI SAN solutions in the form of an iSCSI Storage Exchange kit, offering the highest level of flexibility for IP storage of Microsoft Exchange data. iSCSI today is allowing SMBs to deploy cost-effective IP SANs due to excellent interoperability and manageability.

Robert Lusinsky is application engineering manager of IP storage and Mark Woithe is director of IP storage marketing at Xiran (Irvine, CA)
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Article Details
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Title Annotation:Connectivity; Internet Small Computer Systems Interface
Author:Woithe, Mark
Publication:Computer Technology Review
Geographic Code:1USA
Date:May 1, 2004
Previous Article:Plan for the worst, hope for the best: backup & disaster recovery, part 3.
Next Article:8Gb Fibre Channel is now ratified by the FCIA: so what?

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