HP 2124 ISS Technology Update, Volume 8, Number 3 - Page 2

ISS Technology Update Volume 8, Number 3 VC Flex-10 interconnect module. Using the VC interface, an administrator can set and control the transmit bandwidth available to each FlexNIC. Each dual-port Flex-10 device supports up to eight FlexNICs, four on each physical port, and each Flex-10 Interconnect Module can support up to 64 FlexNICs. Single Root I/O Virtualization (SR-IOV) SR-IOV's ability to scale is a major advantage. The initial Flex-10 offering is based on the original PCIe definition that is limited to 8 PCI functions per given device (4 FlexNics per 10Gb port on a dual port device). With SR-IOV, there is a function called Alternative Route Identifiers (ARI) that allows expansion of up to 256 PCIe functions. The scalability inherent in the SR-IOV architecture has the potential to increase server consolidation and performance. Another SR-IOV advantage is the prospect of performance gains achieved by removing the hypervisor from the main data path. Hypervisors are essentially another operating system providing CPU, memory, and I/O virtualization capabilities to accomplish resource management and data processing functions. The data processing functionality places the hypervisor squarely in the main data path. In current I/O architecture, data communicated to and from a guest OS is routinely processed by the hypervisor. Both outgoing and incoming data is transformed into a format that can be understood by a physical device driver. The data destination is determined, and the appropriate send or receive buffers are posted. All of this processing requires a great deal of data copying, and the entire process creates serious performance overhead. With SR-IOV, the hypervisor is no longer required to process, route, and buffer both outgoing and incoming packets. Instead, the SR-IOV architecture has exposed the underlying hardware to the guest OS, and while the guest OS still employs virtual Ethernet, it is now "paravirtualized." Paravirtualization lets the guest OS translate data by employing a virtual machine monitor (VMM). Calls to the hardware device drivers from the guest OS are replaced with calls to the VMM which handles the data processing tasks formerly performed by the hypervisor. This removes the hypervisor from the main data path and eliminates a great deal of performance overhead. The hypervisor continues to allocate resources and handle exception conditions, but it is no longer required to perform routine data processing. Since SR-IOV is a hardware I/O implementation, it also uses hardware-based security and quality of service (QoS) features incorporated into the physical host server. Summary Advantages associated with using Flex-10 technology are significant. The ability to adjust transmit bandwidth by partitioning data flow makes 10GbE more cost effective and easier to manage. It is easier to aggregate multiple 1Gb data flows and fully utilize 10Gb bandwidth. The fact that Flex-10 is hardware based means that multiple FlexNICs are added without the additional processor overhead or latency associated with server virtualization (virtual machines). Significant infrastructure savings are also realized since additional server NIC mezzanine cards and associated interconnect modules may not be needed. See http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01608922/c01608922.pdf for more detailed information on Flex-10. It is important to note that Flex-10 is an available HP technology for ProLiant BladeSystem servers, while SR-IOV is a released PCI-SIG specification at the beginning of the execution and adoption cycle. As such, SR-IOV cannot operate in current environments without significant changes to I/O infrastructure and the introduction of new management software. Once accomplished, these changes in infrastructure and software would let SR-IOV data handling operate in a much more native and direct manner, reducing processing overhead and enabling highly scalable PCI functionality. For more information on the SR-IOV standard and industry support for the standard, go to the Peripheral Component Interconnect Special Interest Group (PCI-SIG) site at - http://www.pcisig.com. 2