VERITAS Volume Manager 3.5 Administrator's Guide (September 2004)

Chapter 2 86

• Any volume with an entry in the LIF LABEL record must be

contiguous. It can have only one subdisk, and it cannot span to

another disk.

• The rootvol and swapvol volumes must have the special volume

usage types root and swap respectively.

Root Disk Mirrors

All the volumes on a VxVM root disk may be mirrored. The simplest way

to achieve this is to mirror the VxVM root disk onto an identically sized

or larger physical disk. If a mirror of the root disk must also be bootable,

the restrictions listed in “Booting Root Volumes” on page 86 also apply to

the mirror disk.

NOTE If you mirror only selected volumes on the root disk and use spanning or

striping to enhance performance, these mirrors are not bootable.

See “Setting up a VxVM Root Disk and Mirror” on page 87 for details of

how to create a mirror of a VxVM root disk.

Booting Root Volumes

NOTE At boot time, the system ﬁrmware provides you with a short time period

during which you can manually override the automatic boot process and

select an alternate boot device. For information on how to boot your

system from a device other than the primary or alternate boot devices,

and how to change the primary and alternate boot devices, see the

HP-UX documentation and the boot(1M) manual page.

Before the kernel mounts the root ﬁle system, it determines if the boot

disk is a rootable VxVM disk. If it is such a disk, the kernel passes

control to its VxVM rootability code. This code extracts the starting block

number and length of the root and swap volumes from the LIF LABEL

record, builds temporary volume and disk conﬁguration objects for these

volumes, and then loads this conﬁguration into the VxVM kernel driver.

At this point, I/O can take place for these temporary root and swap

volumes by referencing the device number set up by the rootability code.