By Dave Simpson
Earlier this summer, Microsoft announced the availability of its iSCSI software initiator package, which includes a software driver and initiator service. The software works with Windows 2000 client and server versions, Windows XP, and Windows Server 2003 and is available for free download at www.microsoft.com/downloads.
Ratified as a standard by the Internet Engineering Task Force (IETF) early this year, iSCSI enables block-level storage traffic over IP networks, providing an alternative to Fibre Channel for building storage area networks (SANs).
Analysts say that the free drivers and Microsoft's strong support for iSCSI may give the storage networking protocol the shot in the arm that it's been lacking since development began three years ago. (Cisco and IBM submitted an iSCSI draft specification to the IETF in 2000.)
"Microsoft could very well be the catalyst for iSCSI adoption, not just because of the free drivers but also because of their overall support for iSCSI and their testing and certification programs," says John Webster, founder and senior analyst at the Data Mobility Group consulting firm.
In an analysis of Microsoft's iSCSI strategy, Webster states: "Microsoft is breaking down the barriers to iSCSI adoption...because iSCSI solves problems for Microsoft, particularly those related to Exchange [as well as SQL Server] environments. We believe Microsoft can single-handedly create the iSCSI boom that eluded Cisco and IBM." (For more on Webster's analysis of Microsoft's effect on iSCSI, see "Which vendor will save iSCSI?", p. 46.)
The problems that Webster alludes to have to do with the fact that direct-attached storage limits the growth of Exchange databases, which can benefit from SAN-based consolidation of storage and data. In addition, Webster argues that Microsoft "has never been comfortable with the network-attached storage (NAS) alternative in Exchange environments," and that the other alternative—Fibre Channel SANs—is too complex and costly for Microsoft's mass-market strategy.
"Microsoft is highly supportive of iSCSI, in part because it will move some advanced external storage capabilities into the Windows market and lower-priced server segment at price points that haven't been seen before in the storage industry," says Robert Gray, an analyst at International Data Corp., which conducted an in-depth user survey on iSCSI earlier this year.
PBS adopts iSCSI
The Public Broadcasting Service (PBS) has been using beta versions of Microsoft's iSCSI drivers since March. PBS built an IP SAN based on the software drivers and StoneFly Networks' iSCSI-based i1500FS Storage Concentrators (routers) to link "stranded servers" to a Fibre Channel SAN. PBS's dual SANs also include IBM "Shark" and FASt T500 disk arrays, and standard Gigabit Ethernet network interface cards (NICs) from Intel on the four hosts in the IP SAN. In addition to routing, StoneFly's Storage Con- centrator software provides storage provisioning, virtualization, and IP SAN management capabilities.
Applications running on PBS's IP SAN consist primarily of SQL Server databases and a Web-based learning application.
According to Ken Walters, senior director of enterprise platforms at PBS, the key goals behind implementing the IP SAN were reduced costs, improved data availability, and storage centralization.
"iSCSI solved the 'stranded servers' dilemma we faced by making it cost-effective to hook up tier 2 and tier 3 ['non-mission-critical'] servers and development servers to a SAN," Walters explains, adding that the company is pursuing a "peaceful coexistence" strategy with its IP and Fibre Channel SANs.
Walters says that PBS did not encounter any integration or interoperability problems with the iSCSI implementation. "We had none of the incompatibility problems with iSCSI that we had with the Fibre Channel SAN [which was installed almost three years ago]," says Walters.
By 2005, Ethernet network interface cards with software drivers are expected to account for the majority of iSCSI SAN connections, as opposed to more-expensive (and higher-performance) iSCSI host bus adapters.
PBS connected the "stranded servers" to the Fibre Channel SAN via iSCSI because direct Fibre Channel attachment would have been too expensive, according to Walters. (For more information about PBS's iSCSI implementation, see sidebar.)
Microsoft's iSCSI initiator package includes support for data encryption (including Internet Protocol Security [IPSec]), Internet Storage Name Service (iSNS) for clients and servers, management via Windows Management Instrumentation (WMI), and an architecture that aggregates different hardware initiators into a common framework.
The company claims that more than 40 vendors are developing Windows-based applications and storage hardware for iSCSI. It has created an iSCSI Designed for Windows Logo Program to enable hardware vendors to qualify their products with Windows platforms.
Will Microsoft's support spur end-user adoption of iSCSI? IDC's Gray says that it will, but that a number of gating factors remain. One key hurdle is a lack of native iSCSI disk arrays from leading vendors such as Dell, Hewlett-Packard, IBM, and Sun. Gray expects iSCSI disk arrays from some of those vendors near the end of this year, "and by early 2004 the iSCSI market is really going to open up," he predicts.
iSCSI NICs vs. SNICs/TOEs/HBAs
End users who are considering adoption of iSCSI-based IP SANs will have to address the issue of whether to go with free iSCSI software drivers or host cards that offload TCP/IP and iSCSI processing from host CPUs. Using only software drivers enables you to use standard, inexpensive Ethernet network interface cards (NICs).
Depending on the degree of offloading provided, iSCSI cards are variously referred to as storage NICs (SNICs), TCP/IP offload engine (TOE) cards, or iSCSI host bus adapters (HBAs). Pricing for these cards ranges from less than $500 to $900.
The Public Broadcasting Service (PBS), an early adopter of IP SANs, has for now opted to go only with Microsoft's iSCSI drivers and Ethernet NICs from Intel on the four hosts on its iSCSI-based IP SAN, which the company uses to connect "non-mission-critical" servers to its existing Fibre Channel SAN. (For more information on PBS's iSCSI SAN, see the main article.) However, PBS has tested offload cards from Alacritech and Intel. (iSCSI HBAs are also available from Adaptec.)
Ken Walters, senior director of enterprise platforms at PBS, says the company is getting adequate performance from the iSCSI software drivers and NICs, but that the company may upgrade to SNICs in the future. The decision, says Walters, comes down to how much CPU power you have and whether you need support for "dynamic disks" (an advanced formatting option under Windows).
"If your hosts have adequate CPU cycles, there may be no performance difference between NICs and SNICs in an iSCSI environment," says Walters, "but if you don't have enough CPU power you may need to go with a SNIC or TOE card so that the iSCSI and TCP/IP processing doesn't chew up host CPU cycles." The other option in PBS's case is to directly attach the servers to the Fibre Channel SAN, which would provide the best performance but at the highest cost (due to the cost of Fibre Channel HBAs and switch ports).
Another issue is support for dynamic disks. "I need dynamic disks and a volume manager for storage efficiency," says Walters, "and for now the Microsoft iSCSI drivers require a workaround for dynamic disks. With Intel's SNICs, I haven't had any trouble with dynamic disks."
John Webster, founder and senior analyst with the Data Mobility Group consulting firm, believes that most end users will initially go with standard NICs and software drivers. "Most people will opt for the cheapest solution first to see how it works, and if they don't have enough horsepower, they'll go with TOEs."
For a more-in-depth analysis of software drivers vs. offload cards, see "iSCSI software initiators vs. iSCSI host bus adapter adapters," p. 35.