4.7. Enabling Multipath I/O Support

Multipathing is the technique of creating more than one physical path between the server CPU and its storage devices. It results in better fault tolerance and performance enhancement. Oracle VM supports multipath I/O out of the box. Oracle VM Servers are installed with multipathing enabled because it is a requirement for SAN disks to be discovered by Oracle VM Manager.


Any system disks (disks that contain / or /boot) are blacklisted by Oracle VM Manager and are not available for use in an Oracle VM environment.

Multipath configuration information is stored in /etc/multipath.conf and contains specific settings for Oracle VM along with an extensive set of configuration details for commonly used SAN hardware. In most cases the user should not need to modify this file and is advised not to. Examining the contents of the file may be useful to better understand how it works in Oracle VM and what may need to be configured if your SAN is not using multipathing and your LUNs are not appearing.

In case user action is required to enable multipathing, this sections explains how to do so. The required steps depend on the storage hardware implemented. Consequently, the steps below are intended as a guideline and priority should be given to the SAN hardware documentation.


Not all steps apply to your environment. Consult the SAN hardware vendor's documentation for a complete list of steps, the order in which to execute them, and their relevance to your specific environment.

General steps to configure multipathing:

  1. Design and document the multipathing configuration you intend to apply to the SAN hardware used in your Oracle VM environment.

  2. Ensure that the drivers for your Host Bus Adapters (HBAs) are present. If not, install the drivers.

  3. Configure the appropriate zoning on the fibre channel switches.

  4. Configure LUN masking on the storage arrays.

  5. Configure path optimization features (ALUA or similar) on your disk subsystem, if so instructed by your vendor's documentation.

  6. Check the fabric information on each Oracle VM Server that has access to the SAN hardware. Use multipath -ll and related commands.

  7. Make the necessary changes to the file /etc/multipath.conf on the Oracle VM Servers.


    You must make the exact same changes to the multipath configuration file on all Oracle VM Servers in your environment.

  8. Restart the multipath daemon (multipathd).

  9. Check the fabric information again to verify the configuration.

  10. If so instructed by the vendor's documentation, rebuild initrd.

  11. Reboot the Oracle VM Servers to verify that the SAN and multipathing configuration come up properly after a restart.

For detailed information and instructions, consult the SAN hardware vendor's documentation.


Booting from a multipath SAN is supported.