IOV was particularly important, the theory went, as multi-core servers are introduced with increasingly powerful processors, I/O was destined to be the limiting factor in virtualization. As such IOV would deliver performance gains enabling servers to run far more virtual machines more efficiently. "Single Root IOV unburdens the CPU by offloading the cycles that would otherwise be dedicated to the software switches inside of hypervisors," says VanVoros. "This is important for two reasons. First, we can get more VMs on a single server because I have more CPU bandwidth available. Second, for the applications that are virtualized, I may be paying a CPU-based licensing fee on the software, which makes any 'stolen cycles' expensive. Oracle charges for licenses by the core for their database. Those CPU cycles are very expensive," says VanVoros.
Some quick math shows that IOV results in more efficient use of CPU resources. "We did a technology demo with Intel at Intel's Developer Forum last year that showed a 7 to 13 percent reduction in CPU loading on VMware wHen using SR-IOV. The amount of savings depends on how much you are asking the software switch to do, such AS vLAN administration, packet filtering, etc. Our math shows ~5 more VMs per server or you could reserve this for peak demand. So, IOV came in to allow vast numbers of VMs to reside on a 1U physical server; the cost savings were clear from day one," says VanVoros.
In fact, virtualization adoption is still in its infancy making the need for IOV nominal. "Only 16 percent of enterprise workloads are running on virtual machines today" says Gartner analyst Tom Bittman. I/O Virtualization only starts to make sense when 20or 30 VMs are on each server, says VanVoros, then the software switch in the hypervisor consumes a lot of resources. If you have three or four VMs per server, IOV is not all that important. On average, he says that he sees five to eight VMs per server.
Part of the reason for virtualization's extended incubation period has to do with the fact that if you need to reduce server costs, the thing to focus on is application licensing not server hardware. "When you look at licensing in general, the fact that you spent $8,000 on a server can be 10 to 15 percent of the overall server cost," VanVoros says, "So if you're trying to save money by virtualizing applications, you may just dedicate a server for that one application and then have pool of servers for virtualized applications." While servers are not overly expensive and the price is only going down, consolidating them is not going to slash data center costs the way things are working at the moment.
Today, the market for IOV remains largely in high-end computing and biggest virtualization shops. In those markets, engineers are eager to push their hardware with maximum virtualization density and need IOV to support so many VMs, precisely the market where Xsigo fares well. One of Xsigo's first customers was Avaya, who use Xsigo's technology for their developers, to run diverse application environments for R&D scenarios. Using IOV, Avaya has enabled them to test applications without the need to give each developer a number of physical server to play with. Xsigo has built their infrastructure on such high-powered computing by using InfiniBand to promise low latency high bandwidth communication.
