Networking and storage converge on IS-NICs

Posted on January 01, 2002

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By Nancy Marrone

With the onset of iSCSI, a new breed of interface cards is evolving to support block-file transfers over TCP/IP networks. At the Enterprise Storage Group, we believe the term IS-NIC (Integrated Storage Network Interface Card) represents a new frontier, whereby a single adapter can be used for both iSCSI storage traffic and standard Ethernet/IP networking-concurrently. Most other approaches will require both an iSCSI HBA and/or a standard NIC with a driver.

At first, the term iSCSI HBA was used for interface cards supporting iSCSI protocols, but that terminology would only be familiar to those in the storage world, where HBA is a common term.

The TCP/IP networking world uses the term "network interface card" (NIC). In order to adapt to that environment (which iSCSI was developed for in the first place), the industry started using the term "SNIC" (Storage NIC). This defines a card that supports the iSCSI protocol. To support iSCSI, an NIC card only needs to provide the ability for SCSI block commands to be transferred over TCP/IP.

We find that definition to be too broad. For example, it doesn't define if the card is using TCP/IP offload capabilities, or if the full TCP/IP stack is being integrated on the card. Why would these things be important? TCP/IP offload (or acceleration) puts the TCP/IP protocol processing in hardware, as opposed to software. This can relieve the host of up to 90% (in some cases) of its protocol processing requirements. The intent is to greatly reduce the overhead and latency of processing the protocol in software, thus eliminating many of the roadblocks that currently exist for iSCSI to be viable. (TCP/IP is an extremely slow and processor-intensive protocol for storage purposes.)

The term SNIC does not define whether there is TCP/IP offload capability in the card. Beyond that, not all vendors are implementing the full TCP/IP stack in their SNICs. If the stack is not fully integrated, then Ethernet/IP networking features such as fail-over and link aggregation cannot be used. In that case, a server will still need to have two cards: a standard Gigabit Ethernet NIC and a SNIC or iSCSI HBA to support full TCP/IP network functionality.

An IS-NIC incorporates TCP/IP offload features and fully integrates the TCP/IP stack. The term "integrated" refers to the ability to use a single card for standard Ethernet/IP networking and storage networking (block-level iSCSI).

Many interface card vendors targeting this space will be implementing some form of TCP/IP offload, and there will be multiple approaches. There will be arguments about full offload vs. partial offload, but users will focus on performance, feature sets, and price.

The first announcement of an IS-NIC came from Alacritech, but vendors such as Adaptec, Agilent, Emulex, Intel, QLogic, and others will follow shortly.

We believe the iSCSI market will ramp up sharply over the next few years, in part because Ethernet/IP is ubiquitous. However, the acceptance of iSCSI will depend on vendors' ability to enhance the performance of TCP/IP.

Users will benefit from increased TCP/IP performance, but the best feature from an end-user perspective is that they only need to use one IS-NIC to address both their Ethernet/IP networking and storage networking requirements.


Nancy Marrone is a senior analyst with the Enterprise Storage Group (www.enterprisestoragegroup.com) in Milford, MA.


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