Support for the Internet Small Computer System Interface (iSCSI) storage access protocol will be delivered via a free driver for Windows 2000 and later systems, Microsoft has announced. Recently ratified by the Internet Engineering Task Force (IETF), iSCSI allows computers to communicate with block storage devices such as disk arrays and tape units over standard Internet protocols. Microsoft’s support should help establish iSCSI as a standard means of connecting Windows systems to storage area networks (SANs) at lower cost and with a higher degree of hardware interoperability and application support than with the more prevalent Fibre Channel protocol.

Microsoft also announced it will create an iSCSI Designed for Windows Logo Program to enable IHVs to qualify their Windows-targeted iSCSI hardware components.

Cheaper, More Flexible SANs

iSCSI is a protocol that allows compatible hardware to transport block storage data over any IP network, including LANs, WANs, and the Internet, enabling these networks to act as SANs. Unlike the more mature Fibre Channel protocols used in most SANs today, iSCSI traffic does not require special switches or routers, which makes it useful for both local and remote storage access.

In the case of local access, servers and clusters can use iSCSI to connect to storage arrays over common high-speed LAN technologies, such as Gigabit Ethernet. For remote access, servers can use iSCSI to connect to storage over high-speed WAN links, such as synchronous optical network (SONET), T-1, or frame relay, potentially enabling outsourcing of storage services.

In addition, iSCSI can be used by storage devices to mirror data to remote locations, a critical component of disaster recovery protection, and provide access between storage arrays and tape libraries for backup and recovery, either on- or off- premises.

iSCSI traffic can travel over dedicated networks or share media with normal data traffic, as long as sufficient bandwidth is available. It works over both the current Internet Protocol version 4 (IPv4) and the emerging IPv6 protocol, and can be secured using IP Security (IPSec).

Although iSCSI works with conventional network switches and routers, conventional PC network interface cards (NICs) are insufficient. NICs used with iSCSI must be specially designed to offload protocol processing from the server’s or storage device’s CPU to a special coprocessor on the NIC, which also performs encryption and decryption when needed.

Nevertheless, iSCSI offers advantages over the competing Fibre Channel protocol. Fibre Channel is much more expensive to implement, less flexible, and still plagued by poor interoperability, even though it has been widely available for more than five years. To date, more than 60 ISVs and hardware vendors are either planning on developing Windows-based applications and storage hardware products for iSCSI, including all of the big names in storage and networking, such as Adaptec, Brocade, Cisco, Dell, EMC, Emulex, Fujitsu, Hewlett-Packard, IBM, Intel, NEC, Network Appliance, and Quantum.

Microsoft’s Support Crucial

Because iSCSI needs to offload processing to the NIC, the NIC and the operating system must be designed to work together. By creating a standard driver and programming interfaces, Microsoft will make it much simpler for iSCSI NIC vendors to create and test card drivers and obtain full interoperability with other vendors' equipment. By supporting iSCSI, Microsoft will also be able to officially support systems built with certified equipment, which will make it less risky for customers to buy and operate iSCSI-based SANs.

Microsoft's iSCSI driver download will include support for IPSec security, name resolution via the Internet Storage Name Service, management via Windows Management Instrumentation (WMI), and an architecture for aggregating the different hardware components into a common framework.

Availability and Resources

A beta version of the iSCSI driver for Windows 2000 and later systems will be available for download in late Mar. 2003, and the final version is expected to be released in June 2003. The iSCSI Designed for Windows Logo Program will commence at that time.

For more information on Microsoft’s support of SAN technologies, see "Windows .NET Server Supports Enterprise Storage" on page 3 of the Dec. 2002 Update.

For the IETF iSCSI specification, see www.ietf.org/rfc/rfc3347.txt.