On IBM® eServer™ hardware systems, virtual adapters, including Ethernet, Small Computer Systems Interface (SCSI), and serial, interact with the operating system like any other adapter, except that they are not physically present.
The system administrator uses the Hardware Management Console (HMC), Integrated Virtualization Manager, or Virtual Partition Manager to create virtual adapters in order to use virtual I/O devices. Adapters can be added while the system is running. The virtual adapters are recorded in system inventory and management utilities. Converged location codes can be used to correlate operating-system level or partition-level software entities, such as eth0, en0, and CMN21, to adapters. Similarly, the Ethernet adapters are visible in the same way as physical Ethernet adapters.
By default, Virtual Ethernet Media Access Control (MAC) addresses are created from the locally administered range. Using the default MAC addresses, it is possible that different IBM eServer hardware servers will have virtual Ethernet adapters with the same addresses. This can present a problem if multiple, virtual networks are bridged to the same physical network.
If a server partition providing I/O for a client partition fails, the client partition might continue to function, depending on the significance of the hardware it is using. For example, if one partition is providing the paging volume for another partition, a failure of the partition providing that particular resource will be significant to the other partition. However, if the shared resource is a tape drive, a failure of the server partition providing the resource will have only minimal effects on the client partition.
The following table summarizes operating system support for using virtual I/O devices.
| Virtual console | Virtual Ethernet | Virtual disk | Virtual CD | Virtual tape | |
|---|---|---|---|---|---|
| AIX® | Yes | Yes | Yes | Yes (when Integrated Virtualization Manager managed) | Not supported |
| Linux® | Yes | Yes | Yes | Yes | Yes |
| i5/OS® | Yes | Yes | No | No | No |
AIX partitions support booting from virtual devices, including disk boot from virtual disk or network boot from virtual Ethernet.
The firmware running in AIX and Linux logical partitions recognizes virtual I/O and can start the partition from virtual I/O. IPL can be either from the network over virtual Ethernet, or from a device such as virtual disk or virtual CD.
The following table summarizes operating system support for providing virtual I/O to partitions.
| Virtual CD | Virtual console | Virtual disk | Virtual tape | |
|---|---|---|---|---|
| i5/OS | Yes | Yes | Yes | Yes |
| Linux | Yes | Yes | No | No |
| Virtual I/O Server | Yes | Yes | Yes | Not supported |
Version 1.1 of the Virtual I/O Server (08/2004) provides SCSI disk and shared Ethernet adapter function to client partitions.
i5/OS provides disk, CD, tape, and console. i5/OS uses the same network server storage and network server description that it uses on IBM eServer i5 systems.
Virtual I/O configuration is a combination of HMC and operating system configuration, whereas adapter configurations are made in the HMC. They include:
After the HMC configuration has been made, the partition is aware that virtual adapters and operating system configurations can be made. For Linux partitions, virtual adapters are listed in the device tree. The device tree contains Virtual SCSI adapters, not the devices under the adapter.