Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Chapter 2, Administering Disks
Rootability
83
Sharing (CDS) feature, cannot be used. The vxcp_lvmroot and vxrootmir
commands automatically configure a suitable disk type on the physical disks that you
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 83 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 84 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), pdc(1M) and
isl(1M) manual pages.
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 bootdg 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.