Xsigo takes an interesting approach in addressing the I/O concerns.
The solution is to virtualize server I/O. That is, turn normally fixed and static I/O channels, host bus adapters, and network interface cards into more dynamic resources whose capacity can expand and contract based on virtual server needs. If I/O virtualization could be achieved, it would resolve a persistent problem server administrators have as they stack virtualized applications on the same hardware. Until virtualized I/O becomes commonplace, applications with heavy or fluctuating I/O demands aren't being virtualized, lest they end up causing I/O backups.
Two early solutions have emerged and more are sure to follow. Startup Xsigo off-loads I/O traffic to an attached appliance that virtualizes it (see diagram, p. 20). The approach requires replacing standard HBAs and NICs on the server with Xsigo custom cards and investing in the Xsigo appliance. Pricing starts at $30,000.
Xsigo's appliance can generate up to 16 usable channels of I/O, feeding storage traffic to a Fibre Channel network or LAN traffic to an Ethernet network. It also can monitor workloads and assign more capacity to the VMs that need it most. Virtualizing I/O helps balance the virtual machine workload, letting applications that generate heavy I/O traffic during the night work alongside other applications that only experience occasional spikes in activity.
The virtual I/O appliance approach also reduces network cabling in the data center and lets IT administrators buy smaller, more energy-efficient servers that have fewer networking ports and bulky HBAs and NICs.
Virtualizing I/O makes data centers more efficient and balances I/O for virtual machine workloads, says Ray Lane, former president of Oracle and an investor in Xsigo. "Inflexible architectures contribute to the low resource utilization and waste scarce power, space, and cooling resources," Lane says.
Another way of virtualizing I/O is done in the standard HBA or NIC, without resorting to an add-on appliance. Industry group PCI-SIG came up with the SR-IOV standard, which virtualizes high-speed, 10-Gbps Ethernet for future NICs and HBAs.
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