IP storage NICs may disappoint

Companies expecting to use IP networks to route storage and network data may be disappointed when they see the problems caused by new adapters that are supposed to make this scenario work.

As early as next month, Intel and Adaptec will ship some of the first IP storage (iSCSI) network interface cards (NIC) designed to transport block-oriented storage and network data. To achieve the speed of rival Gigabit Ethernet and Fibre Channel yet still carry gobs of data, these adapters fully off-load TCP/IP processing from the host operating system and bundle it on the NIC hardware with the iSCSI storage protocol.

The TCP/IP offload is the crux of the routing and management problems IT managers will encounter when they install these NICs in Windows NT Servers, and to a lesser degree in other networks. The NIC vendors promise fixes in future upgrades.

In off-loading TCP/IP from the operating system where it typically is configured, the iSCSI adapter can't be used to perform alternate pathing or load balancing with Gigabit Ethernet adapters co-residing in a server. They also can't be assigned to the same NT domain as the Gigabit Ethernet adapter, where they can be managed more easily.

Alternate pathing and load balancing place two adapters in a server, where they balance the network traffic and provide failover capabilities for each other in the event that one of the adapters fails.

That has Bill Manning worried. Manning, associate director of technical services for the Plumbers & Pipefitters National Pension Fund, says iSCSI is a natural candidate for implementation on his network because it installs, manages and troubleshoots in the same manner as Gigabit Ethernet.

"[ISCSI lets] you keep your Ethernet knowledge without going to a Fibre Channel network," he says. "We've been on Ethernet for a number of years now, so there is a large knowledge base out there [among the technicians]."

Manning, who administers separate Gigabit Ethernet and Fibre Channel storage-area networks (SAN), uses alternate pathing and load balancing in most of his Windows 2000 and NT servers, which makes the adapter limitations important to him. "You want to reduce the single point of failures in the network," he says.

In addition, in NT networks, placing two nonroutable adapters in the same server requires the creation of two domains, he says. "It's a problem having two domains in the same server, getting the adapters to recognize each other. [Domain] management conflicts would be considerable."

In addition, Microsoft has declined to certify the Intel and Adaptec adapters under its Windows Hardware Quality Labs (WHQL), a must for many network managers.

"With respect to the TCP/IP offload, Microsoft has to [separate] TCP/IP from its operating system and make it run with iSCSI adapters," says Ram Jayam, vice president at Adaptec. "Because certification is a sticky mess and Microsoft does not support [iSCSI] today, moving forward we'll all have to wait and see how they move."

Microsoft says it is working on adding iSCSI capability to its NT and .Net server operating systems, a need it recognized in a meeting with storage experts three months ago. Once that is completed, it could award WHQL certifications. Microsoft says it does not expect WHQL certification until after the .Net Server ships, slated for the first part of next year.

In the meantime, to get the iSCSI and Ethernet adapters to work compatibly, vendors need a special middleware driver that lets the TCP/IP stack on the iSCSI adapter communicate with the TCP/IP stack in the operating system, Jayam says.

Operating systems other than NT have fewer problems of this nature with routing and have less need for the special driver because they are more configurable, experts say.

Adaptec and Intel have promised new iSCSI adapters in the second half of this year that will overcome the routing problems.

"An iSCSI adapter should do more than iSCSI," says Mark Bakke, chief architect at Cisco and co-author of the iSCSI specification. "All iSCSI adapters should support any IP traffic at the same time, using the same IP addresses and the normal [operating system] stacks."

Bakke says it should be unnecessary to duplicate the iSCSI and Gigabit Ethernet adapters in the server just to achieve load-balancing and traffic management or to have separate networks for storage and other network traffic.

"If I have a server that requires redundant interfaces, I can do this with only two adapters, using both for storage and network traffic," Bakke says.

The iSCSI draft is being reviewed within the Internet Engineering Task Force for possible standardization as soon as this summer.

Advocates of iSCSI are excited by its promise to provide an alternative to separate, expensive Fibre Channel SANs. They praise iSCSI as a familiar technology that doesn't require retraining, infrastructure additions or rewiring, and that it lets them efficiently transport SCSI data across a Gigabit Ethernet network.