7. I/O Virtualization
In this chapter the possibilities of virtualizing I/O with PowerVM are presented. The two central components are the POWER hypervisor and the so-called virtual I/O server. The POWER Hypervisor has functions that make it possible to provide virtual processors, virtual SCSI adapters and virtual FC adapters for LPARs. It implements the communication and data transport of the virtual adapters within a POWER system. The virtual I/O server is a special LPAR on the managed system with an AIX operating system that has been specially expanded for virtualization. The physical adapters (Ethernet, SCSI, FC) are assigned to the virtual I/O server, which takes over the transport of the data between physical adapters and virtual adapters.
As soon as a managed system is powered on, the POWER hypervisor is active. The hypervisor provides the following virtual adapter types especially for the virtualization of I/O:
- virtuelle serial adapters (for client and server), thereby providing consoles for the LPARs
- virtual Ethernet adapters (with and without trunking), with support of IEEE 802.1q VLANs and QoS
- virtual FC adapters (for client and server), so that SAN LUNs can be made available directly to a client LPAR (N_Port-ID virtualization)
- virtual NIC adapters (for client and server), which allows the use of SR-IOV with automatic failover for Ethernet
- virtual SCSI adapters (for client and server), LUNs, logical volumes or files can be mapped as disks to virtual SCSI server adapters
In addition, the POWER Hypervisor implements virtual Ethernet switches. These connect LPARs to one another on the same hardware, and in combination with the virtual I/O servers, also allow connections to external networks, without requiring a physical Ethernet adapter for the client LPAR.
The virtual I/O servers complement the functionalities of the POWER hypervisor by realizing the connection between the virtual resources of the hypervisor and the physical adapters of the hardware. This is achieved, among other things, by
- Shared Ethernet Adapter (SEA)
- NPIV mapping
- VSCSI mapping
- vNIC backing devices
Figure 7.1 shows the interaction between the POWER hypervisor and the virtual I/O server for virtual Ethernet and virtual FC. The virtual Ethernet adapters of the client LPARs have a connection to a virtual Ethernet switch (implemented by the hypervisor). The virtual I/O server is also connected to the internal virtual Ethernet switch by a virtual Ethernet trunking adapter. On the virtual I/O server, a so-called shared ethernet adapter enables a connection between the virtual Ethernet trunking adapter and a physical ethernet port and thus the connection to the outside world. The shared Ethernet adapter is a layer 2 bridge implemented by software on the virtual I/O server.
To access disks, the two LPARs shown, each have a virtual FC client adapter; these are connected to their counterpart, the virtual FC server adapter on the virtual I/O server. The one-to-one connection is provided by the hypervisor. The hypervisor transports the data between the client and server adapter. The connection to a physical FC adapter is then made by mapping the virtual FC server adapter to one of the physical FC adapters on the virtual I/O server. NPIV is used for the mapping (N_Port-ID Virtualization). SAN LUNs can then be mapped directly to the WWPNs of the virtual FC client adapter.