In June 2003, Microsoft released the first component of its Windows iSCSI support—Windows iSCSI Software Initiator, which supports Windows Server 2003, Windows XP Service Pack 1 (SP1), and Windows 2000 SP3 (client and server). These Windows OSs use the package to connect to iSCSI targets that support iSCSI. The iSCSI Software Initiator has three components: user-mode management tools and APIs, the user-mode iSCSI Software Initiator service, and one or more kernel-mode initiator drivers. The management API interfaces and the kernel-mode initiator driver interfaces are well defined; hardware and software vendors can leverage the interfaces to produce value-added components. The package also includes a software-based iSCSI kernel-mode initiator driver that uses the Windows TCP/IP stack and the NICs that Windows supports. Vendors can develop specialized iSCSI hardware (iSCSI HBAs) and write SCSI or Windows 2003 Storport miniport drivers for the iSCSI Software Initiator service to use. Microsoft provides a Device Driver Kit (DDK) for this purpose.
Because the iSCSI Software Initiator service coordinates iSCSI management in Windows, a storage-management application vendor can include iSCSI support in its management application by writing directly to the Windows iSCSI management interfaces. The application can then use a common approach to manage both hardware and software initiator drivers in Windows. The second component of Microsoft's iSCSI support is the Microsoft iSNS Server, which Windows clients and servers use—by means of a gateway—to discover and register iSCSI and Fibre Channel devices on the network. Microsoft claims that the iSNS Server is extremely scalable and that it supports IPSec for storage management and data security. Microsoft provides these iSCSI components free as separate downloads; they aren't included in the box with Windows.
Microsoft seems ahead of most of its competitors when it comes to iSCSI, a technology that's unproven and therefore uncertain. This new technology faces concerns that any new technology faces—concerns such as vendor support, security, and interoperability—and Microsoft's proactive support for the technology will help ensure that the company doesn't get caught off guard, as it did when NAS and SAN technologies became available and Microsoft didn't yet support the technologies. The company is developing strict guidelines and certifications for iSCSI products. For example, Microsoft will leverage the Designed for Windows logo program for iSCSI, and vendors who want the company to support their solutions must pass the program's certification requirements. Microsoft has already tested applications such as Exchange and SQL Server and will support vendor solutions that are logo certified.
Within the next few years, iSCSI's cost efficiency and capabilities should make it a widely used storage-networking technology. When that happens, Windows administrators will be able to deploy iSCSI solutions with more confidence and support from Microsoft than they had with NAS and SAN. For more information about iSCSI, see "iSCSI Resources," page 17.