Voltaire Mates InfiniBand & iSCSI

"Abomination!" the Jacobins are thundering from the pulpits. "Contrary to Nature!" Or something... Startup Voltaire Inc. has created a weird hybrid to provide storage connectivity to its InfiniBand switch: It's running iSCSI over InfiniBand to let servers access back-end Fibre Channel storage systems (see Voltaire Bonds iSCSI With InfiniBand).

Voltaire is the first IB switch maker to adopt iSCSI, an IP-based protocol for transmitting SCSI storage traffic. The company has also developed a Fibre Channel module for its switch to provide access to existing FC SAN storage. This thing is just begging for a new moniker -- InfibriSCSI, anyone? (Too Polish?)

But it isn't using TCP/IP for the transport layer. Instead, Voltaire is using the low-level Remote Direct Memory Access (RDMA) features built into the InfiniBand protocol. That eliminates the performance bottlenecks associated with iSCSI today, providing very low CPU overhead while reaping the benefits of an industry standard, the company says.

Asaf Somekh, director of marketing at Voltaire, says running iSCSI over InfiniBand eliminates the need for an additional storage adapter in a server that's connected to an IB fabric, instead of requiring a separate Fibre Channel host bus adapter (HBA).

He adds that 4x (10 Gbit/s) InfiniBand delivers roughly five times the aggregate throughput of 2-Gbit/s Fibre Channel. "We're seeing some environments where customers are putting three [Fibre Channel] HBAs in the server because they weren't getting enough throughput," Somekh says. "If you look at the aggregated approach, building on the 4x InfiniBand, you're not limited."But Voltaire concedes that not many will bother with its iSCSI-to-InfiniBand-to-Fibre-Channel offering unless they already have decided to go with InfiniBand. "The assumption today is that the customer has selected InfiniBand to improve the performance of their database," says Somekh.

All the same, observers say, Voltaire's iSCSI-over-InfiniBand system is impressive in that it delivers iSCSI in a way that meets the needs of the data center.

"They may have come at it orthogonally, but the novelty of this solution to me is that they've created what is probably the highest-performing iSCSI solution in the market," says Arun Taneja, founder of consulting firm Taneja Group.

While Voltaire may be the first IB vendor to move to iSCSI, it's actually trailing two competitors, InfiniCon Systems Inc. and Topspin Communications Inc., in delivering storage connectivity. Topspin is using SCSI RDMA Protocol (SRP) over InfiniBand for storage connectivity; meanwhile, InfiniCon uses its own proprietary InfiniFibre protocol -- which it says supports SRP -- to provide access to FC storage.

Somekh notes that iSCSI is a much more widely supported protocol -- which means applications won't need to be rewritten to support it. He says Voltaire's iSCSI implementation works with the Microsoft Corp. (Nasdaq: MSFT) Windows iSCSI initiator today."We're reusing the stuff that's available today," he says. "Customers don't want to have to manage a new protocol."

Meanwhile, Voltaire is providing FC connectivity through four-port Fibre Channel blades, providing up to 96 ports in a single chassis. The FC blades, which use silicon developed by QLogic Corp. (Nasdaq: QLGC), will be generally available in the fourth quarter of 2003. Pricing was not available.

The Bedford, Mass., startup is also working with StoreAge Networking Technologies Ltd. to integrate StoreAge's virtualization software with its switch, so that servers in the InfiniBand fabric see multiple back-end FC or IP SANs as integrated volumes.

Todd Spangler, US Editor, Byte and Switch