For me, SDN products expand the control plane so that a single controller can manage traffic flows through multiple switches, as OpenFlow products like VMware’s latest acquisition, Nicira, does. Valuable as Xsigo’s technology may be, SDN it isn’t.
To date, Xsigo is the most successful of the external I/O virtualization vendors that popped up a few years ago. While some of its competitors, like Aprius and Virtensys, tried to generally virtualize shared I/O devices, Xsigo stuck to the basics, allowing multiple servers to share 10-Gbps Ethernet and Fibre Channel cards in its Fabric Director.
There's a lot to like in the Xsigo products, especially in large service provider data centers where Xsigo has some success, with about 300 customers. Each server needs just one or two relatively affordable, 40 or 56 Gbps InfiniBand connections to the Fabric Director. Software in the Fabric Director then creates virtual channels or virtual networks over the InfiniBand links. East-West traffic between servers connected to the same Fabric Director has substantially more bandwidth than even 10-Gbps data center networks. The servers also share 10-Gbps Ethernet and Fibre Channel connections from the Fabric Director to external devices.
As a result, a data center with Xsigo Fabric Directors can be reconfigured for different cloud-like applications entirely from the operator console without the hassle and expense of re-cabling.
While Aprius and Virtensys failed in the marketplace, some other vendors thought enough of their PCI-e-centric technology to pick it up at liquidation sales prices. Fusion-io acquired some key staffers, patents and other intellectual property from Aprius when it failed, although co-founder Peter Kirkpatrick became a principal engineer at Violin Memory. Virtensys’ technology ended up in the hands of SSD vendor Micron. Of course, these vendors are on everyone's short list to come up with an ultra-low-latency shared flash memory system to compete with EMC’s promised Project Thunder.
The only external I/O virtualization vendor still around is NextIO, which has been active in GPU computing markets and has a shared SSD cabinet solution called vSTOR.
Xsigo’s use of InfiniBand is a good fit with Oracle’s Exadata and other clustered solutions. External I/O virtualization is still just an access layer solution, and Oracle’s networking portfolio is still thin compared with Dell or HP.