Microsoft is supporting iSCSI SANs using clustering under two different programs. The reason for this is that some Windows iSCSI SANs have been built with up to eight nodes, but the first full release of iSCSI for Microsoft's Cluster Server 2003 will only support two nodes.
Microsoft explains that it hasn't done enough testing with clusters of more than two nodes to support them effectively. In addition, Microsoft's SCSIport, part of the company's iSCSI stack, does not support clusters with more than two nodes because it does not handle individual LUN reset, which causes issues with disk failovers. Microsoft is working to provide eight-node cluster support quickly after the first release of iSCSI Cluster Server 2003.
As a result, Microsoft's official support program will only apply to two-node clusters while the interim support program will continue to support clusters with up to eight nodes -- under certain conditions. First, of course, the iSCSI hardware must be qualified under the Designed for Windows logo program. The other conditions are that interim support will continue until six months after the release date of Windows 2003 Service Pack 1, that the customers will upgrade to SP1 within nine months of its release, and that the vendors submit their cluster configuration for qualification before the deadline expires.
For more information:
Crash Course: iSCSI
About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80 K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last 20 years he has been a freelance writer specializing in storage and other computer issues.