New I/O Subsystem Attributes Can Improve Booting Speed

Three new I/O subsystem attributes control path registration during the boot process, allowing systems with multiple paths to a large number of devices to boot faster. The following list provides a brief description of these attributes. For additional information and settings, see the revised sys_attrs_io(5) reference page delivered in this kit.

boot_wait_hwc_reg
When disabled, causes a boot to the login prompt without waiting for hwc path registrations.
hwc_reg_cmplt_notify_type
Controls how you get notified when device registration is done.
hwc_registration_complete
Proves a query to determine if hwc path registration is complete.

By default, booting will wait for all hwc registrations to be completed. However, you can force the boot process to complete to the login prompt earlier by changing boot_wait_hwc_regs to 0. In either case hwc_registration_complete can be queried. This will be set to 1 as soon as registration is complete. In addition, you can also choose to receive a console message, an EVM event, or both when all paths have registered.

To get the biggest speed improvement when booting, you can elect to finish booting without waiting for path registration, which is not needed to access the storage subsystem (for example, an Oracle® database). However, if you do this, you temporarily have an incomplete hierarchy view from the commonly run hwmgr command.

Each of the following actions can help you determine when to run the hwmgr command in order to see the complete hierarchy:

Enable the EVM notification option, log in, and start evmwatch to look for the EVM event, although the EVM event could have already occurred by the time you log in.
Enable the console log message notification option and look in the messages file for the message.
Query sysconfig to ensure the I/O hwc_registration_complete attribute is set before proceeding. This action can be used regardless of how you set the notification option.