PCIe to the Virtual Rescue

Arthur Cole

We've been talking about the impact that virtualization and multicore processing are having on the network infrastructure of the enterprise all week, so it's only right that we take a look at one of the crucial pieces of technology aimed at combatting I/O bottlenecks: PCI Express.

 

PCIe is showing up more and more on the storage networking side of the house. A number of new storage controllers hit the market in recent days sporting either PCIe or the latest PCIe II iteration.

 

Emulex, for example, has the IOC 3532 PCIe-based host bus adapter, which is now supported by the HP Integrity rx7640 and 8640 servers along with the high-end Integrity Superdome server. With it, Integrity users gain a wide range of Fibre Channel SAN solutions through the HP-UX 11i and OpenVMS operating systems.

SuperMicro supports PCIe 2.0 on its 6015TW SuperServer board, doubling bandwidth from the 2.5 Gbps of the PCIe 1.1 standard to 5 Gbps. The board can be outfitted with two sets of dual Gigabit Ethernet ports or two Mellanox 20 Gbps Infiniband ports.

 

And the PMC-Sierra Tachyon quad 8G Fibre Channel controller we mentioned earlier in the week includes PCIe 2.0 to provide eight lanes of 5 Gbps bandwidth. With four channels of 8 Gbps data, the system provides 6.4 GBps of total throughput and 1.4 million IOPS.

 


But even these devices might be outclassed in the near future. The PCI Special Interest Group, says the EE Times, is already working out new feature extensions for the 2.0 specification. These include support for cache-coherent transactions, virtual memory and multicasting. An initial proposal is due by April, with ratification possible as early as June.

 

The real action, though, is due in 2009 when the SIG is planning to release PCIe 3.0, offering up to 8 gigatransfers per second without the clunky 8b/10b encoding scheme that currently eats up about 20 percent of your processing overhead. That should effectively double performance without losing backward compatibility with current PCIe implementations.



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