VERITAS Volume Manager 4.1 Administrator's Guide

Chapter 2 89

specify are to be used as VxVM root disks and mirrors.

• The volumes on the root disk cannot use dirty region logging (DRL).

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 89

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 90 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.

When the kernel has passed control to the initial user procedure, the VxVM conﬁguration

daemon (vxconfigd) is started. vxconﬁgd reads the conﬁguration of the volumes in the

rootdg disk group and loads them into the kernel. The temporary root and swap volumes are

then discarded. Further I/O for these volumes is performed using the VxVM conﬁguration

objects that were loaded into the kernel.