The latest on iSCSI

Storage-area networks aren't just for the biggest companies manned with Fibre Channel experts anymore. Availability of iSCSI products opens the SAN door to companies of all sizes.

IT departments that go the SAN route gain unprecedented efficiencies in managing their data and storage over the direct-attached model. On a SAN, users can access shared storage using block-level protocols. But until recently, SANs have mostly meant the use of Fibre Channel technology.

Enter the iSCSI protocol, a melding of two standard technologies that have been available for more than 20 years. ISCSI provides the rules by which software or devices receive SCSI commands and data and repackages them into TCP/IP commands and data for movement across an IP network. Cisco, IBM and start-up Nishan Systems rolled out iSCSI products early last year, making it possible to build native IP-based SANs and mixed Fibre Channel-to-IP SANs.

Enterprise benefits

In a native iSCSI SAN, the application host transmits iSCSI packets, or bundles of data, across an IP network to an iSCSI storage device. A native iSCSI SAN provides the high availability, increased application uptime, ability to expand storage capacity without disruption, efficient storage utilization and higher capacity-to-staff ratios commonly associated with Fibre Channel SAN deployments, but for significantly less money.

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An iSCSI SAN is less expensive to deploy than one based on Fibre Channel for two reasons. The first is that minimal additional hardware is required for an iSCSI SAN. IT departments won't need to buy new host bus adapters, network interface cards, or a separate IP network for storage (although it is highly recommended for performance reasons, as an optical network). However. if Fibre Channel storage or SCSI devices will be used on the iSCSI SAN, a router or bridge for translating iSCSI packets into their respective Fibre Channel or SCSI packets will be needed.

The second reason is that IT workers skilled in IP networks are abundant and generally less expensive to hire than people who know Fibre Channel. Provisioning a native iSCSI SAN means installing an iSCSI device driver (which vendors provide at no charge), attaching an iSCSI disk to the network, configuring the disk and mounting the disk partitions as if they were local drives - straightforward tasks for today's network and systems administrators.

The iSCSI entry point

Small to midsize businesses and departments are embracing native iSCSI storage products. For example, E-office, a consulting firm in Huis ter Heide, Netherlands, moved from a network-attached storage (NAS) infrastructure to a native iSCSI SAN primarily because it wanted all internal servers and storage managed consistently, but its Microsoft Exchange server wouldn't work in the NAS environment. Today, E-office performs all development and solutions testing, as well as e-mail, using the iSCSI SAN. The firm now clusters its Exchange servers, which it couldn't do easily before, says Jorn Bijnsdorp, infrastructure consultant at E-office.

"We are looking for flexibility in storage without the cost and complexity of a [Fibre Channel] SAN," Bijnsdorp says.

In its iSCSI SAN, E-office supports 24 IBM xSeries 330 servers, using software iSCSI drivers, with two 200i iSCSI storage subsystems configured with 500G-byte RAID5e disks. It created a separate LAN for storage, primarily for security reasons - Bijnsdorp says he was worried about someone snooping IP packets.

ISCSI for disaster recovery

Among the Fortune 500, an iSCSI configuration gaining popularity is the combination of Fibre Channel and iSCSI to provide remote data replication for disaster recovery. In this environment, users have built a Fibre Channel SAN infrastructure to access primary storage repositories. Alternatively, they require the broader capabilities found in many Fibre Channel disk subsystems but are restricted by Fibre Channel's 6.2-mile distance limit. Fibre Channel-to-iSCSI lets them span distances required for disaster recovery.

Komatsu America, a manufacturer of construction and mining equipment in Vernon Hills, Ill., went with a Fibre Channel-to-iSCSI setup to accommodate storage data and disaster recovery for its extranet, a chief tool for distributors, says Dave Mucha, Webmaster with Kumatsu. It wanted to accommodate the extranet's rapid growth while keeping an overwhelming amount of data on a secure and reliable external storage system, such as IBM's Shark Enterprise Storage Server, he says.

"Since the deployment of a SAN environment can be lengthy and expensive, we were looking for alternatives to handle the storage needs of our applications servers and eventually the back-end systems that support them. ISCSI was the most cost-effective solution, as well as the most flexible," Mucha says.

Komatsu uses Fast Ethernet and Gigabit Ethernet switches and a pair of Cisco SN 5420 IP storage routers connected to a Fibre Channel-attached Shark to provide flexible connectivity for the Web servers. Once the storage was accessible to the IP network, the company could then provide a disaster-recovery site because, as Mucha says, "It takes only minutes for a server to connect to the Cisco SN 5420 and access the information on our [Shark]."

No doubt, the Fibre Channel SAN market will continue to provide high-end services for the data center. But as more iSCSI products become available, from companies such as Adaptec, Alacritech, FalconStor and Hewlett-Packard, the benefits of iSCSI SANs will become attainable by small to midsize businesses and departments within large companies.

Skamarock is a senior analyst with Enterprise Management Associates in Boulder, Colo., and co-author of Network World's "Storage in the Enterprise" newsletter. She can be reached at askamarock@enterprisemanagement.com.

Related links

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