Since much of the server-based storage targeted for consolidation on Internet Protocol storage-area networks (SAN) resides on departmental servers running Windows, Microsoft Corp.'s commitment to iSCSI has been key to the success of IP SANs so far. The company began offering an iSCSI driver, or "initiator," for Windows 2000 Server, Server 2003 and XP Pro shortly after the standard was final in 2003. In February, Microsoft stated it would release late a new version that supports multipathing, a technology common in Fibre Channel SANs that supports load balancing and fail-over by allowing multiple connections, or paths, between servers and storage devices. Previously, Microsoft offered only multipath I/O (MPIO) for Fibre Channel, although Network Appliance Inc. and EqualLogic Inc. adapted it for their iSCSI products. Microsoft's goal is to simplify block-based networked storage by providing a universal initiator and MPIO interface for Windows servers. "In the Fibre Channel world, there are a lot of proprietary solutions, and they can get quite difficult to troubleshoot," says Claude Lorenson, a senior product manager at Microsoft's Windows Server division. To avoid that situation, Microsoft will support only its own MPIO mechanism for iSCSI, although Lorenson says it will continue to support "legacy" MPIO schemes for Fibre Channel.