Microsoft adds high-availability features to iSCSI

Version 2.0 of Microsoft's iSCSI software initiator will support failover, load balancing and additional error recovery levels to support high-availability iSCSI SANs.

Microsoft Corp. announced that Version 2.0 of its iSCSI software initiator for Windows servers has been released to manufacturing and will be available for download by mid-April.

Microsoft estimates that there have been approximately 20,000 downloads of Version 1.0 and around 3,000 users are running applications on iSCSI using its initiator. Almost a 1,000 users have downloaded the beta of Version 2.0.

"iSCSI is finally being deployed and in big numbers now," said Bill Terrill, senior analyst with the Burton Group. He recently spoke with a global oil company that intends to transfer all 1.7 petabytes of its storage, barring a couple of terabytes that absolutely must remain on Fibre Channel, to iSCSI. "They have some requirements for high transaction rates, but for everything else, iSCSI will do it," he said. Unfortunately, the company is not ready to go public on this news yet.

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Users can expect several improvements in the second version of Microsoft's initiator, including integration with Microsoft's Multipath I/O (MPIO), support for all error recovery levels and more features in the GUI to lessen the scripting required.

"The focus in this release was on making iSCSI more resilient and easier for customers to deploy high-availability features," said Claude Lorenson, senior product manager of storage technology in the Windows server division at Microsoft.

Integration with MPIO enables multipathing, or the ability of a server to use more than one read/write path to a storage device. It's a high availability option that provides fault tolerance against single points of failure in hardware components. Multipathing can also provide load balancing of I/O traffic to improve system and application performance.

"It's important for iSCSI as it means that you can now configure a dual-pathed iSCSI server for load balancing and high availability … Previously MPIO only focused on Fibre Channel," said Greg Schultz, senior analyst at the Evaluator Group. V2.0 of the initiator includes an iSCSI Device Specific Module to enable the multipathing support. "There will be no other multipathing for iSCSI, only the Microsoft version," noted Lorenson.

In conjunction with the MPIO integration are improvements to the error recovery feature. Version 1.0 of the product supported error recovery level zero while Version 2.0 supports levels "one" and "two". Basically, these extra levels dictate the behavior of how a target and the initiator work together in different scenarios: For example, what should happen when a target gets disconnected. "It makes it easier when there is an error to go back to the session where you were," Lorenson said.

A capability called "event tracking", that's been available in the operating system and is now in the initiator, lets users pinpoint problems in the SAN by tracing and capturing communication between devices. Microsoft also announced support for x64 servers and IPv6 in Version 2.0.

Microsoft concedes that while improvements to the iSCSI software initiator are important, it would be even better for users if this capability were folded into the operating system -- that way users have less work to do. Lorenson said a new version of the operating system comes out every two years, this functionality is about two to three versions out. "Out-of-band releases have some advantages," he said. "You can more quickly add QFEs and bug fixes, whereas if the functionality is tied into the kernel it takes a much longer time to release." [Ed note: QFE means quick fix engineering and is common parlance in Microsoft circles.]

The company recently hosted an iSCSI plugfest attended by most of the major iSCSI vendors. Companies that have qualified their iSCSI products and support the new 2.0 release of the Microsoft iSCSI software initiator include: Adaptec, ATTO, Broadcom, Crossroads, Cisco, EqualLogic, EMC, Falconstor, HP, Intel, Intransa, Lefthand Networks, Network Appliance, Promise Technology, QLogic, SpectraLogic, SANrad, Stonefly Networks, and String Bean Software.

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