Microsoft Boosts SAN Availability with iSCSI Initiator 2.0

by Alex Woodie

Microsoft last week announced the pending delivery of a new version of its iSCSI Initiator software that will give Windows server users new storage resiliency features. With support for multipath I/O, among other features, iSCSI Initiator 2.0 will help Windows server shops take advantage of high availability and load-balancing capabilities that were previously the domain of expensive Fibre Channel-based storage area networks.

Based on good old Internet Protocol (IP), the relatively young Internet Small Computer System Interface, or iSCSI, storage protocol gives users the capability to build sophisticated storage area networks (SANs) on top of existing Ethernet networks and at a substantially lower cost than SANs based on the Fibre Channel protocol, which require investment in new Fibre Channel compatible hardware. While the promise of iSCSI has been large, the market has been relatively slow to adopt it, but that started to change at the end of 2004.

Microsoft shipped iSCSI Initiator 1.0, its first iSCSI deliverable for Windows Server 2003, Windows 2000, Windows XP, and Windows Storage Server 2003, in the summer of 2003. According to Microsoft, iSCSI Initiator 1.0 has been downloaded about 20,000 times, and there are about 3,000 organizations using it in production--barely a drop in the bucket of Windows server users.

Microsoft hopes that will change with iSCSI Initiator 2.0. The software, which Microsoft plans to make available for download from its Web site in mid-April, will support new resiliency features tailored to higher-end users. Chief among the new features is a new iSCSI Device Specific Module (DSM) that makes it easy to enable Microsoft Multipath I/O (MPIO).

Multipathing in Windows enables a server to use more than one path to read and write to a storage device, and provides a form of fault tolerance against hardware failure. It can also be utilized for load balancing and improving the performance of systems and applications, Microsoft says. In addition to the Microsoft DSM, the company will also allow third-party vendors to create their own DSMs that plug into its MPIO architecture.

Multipathing has been a feature in Fibre Channel SANs, and while it's unlikely that large corporate customers will rip out their existing Fibre Channel SANs to implement a SAN based on Microsoft's new iSCSI implementation, it does provide another option for small and medium sized businesses (SMBs) that are looking to install a SAN to ease storage requirements for their Windows servers.

Other new features in iSCSI Initiator 2.0 will include support for level 1 and level 2 error recovery (previously only level 1 error recovery was supported), a more advanced GUI with "event tracking," and support for the upcoming Windows Server x64 Editions operating system.

The market for iSCSI devices picked up considerably in the fourth quarter of 2004, and was driven mostly by sales of midrange SANs priced between $15,000 and $149,999, according to IDC's "Worldwide Quarterly Disk Storage Systems Tracker" report released earlier this month. IDC says sales of iSCSI-based SANs increased by 32 percent last quarter compared to the third quarter of 2004, and the total market for iSCSI-based SANs topped $100 million for all of 2004. The iSCSI SAN vendors with the biggest market shares were Network Appliance with 38.9 percent of the market, and EMC with 25.6 percent of the market, according to IDC.

As it did for its first generation iSCSI initiator, Microsoft is working with storage hardware and software vendors to get them certified for iSCSI Initiator 2.0. In November, the company launched an iSCSI "Plugfest," which it says was attended by all the major vendors of iSCSI devices. Vendors that already support the iSCSI Initiator 2.0 include Adaptec, Broadcom, Crossroads, Cisco, EqualLogic, EMC, Falconstor, Hewlett-Packard, Intel, Intransa, Lefthand Networks, Network Appliance, Promise Technology, QLogic, SpectraLogic, SANrad, StoneFly Networks, and String Bean Software.

For more information and downloads, visit the Microsoft Storage Technologies iSCSI Web page.