Installation guide

Mirroring Root and Primary Swap
HP-UX version 11.00.03 Mirroring Data 4-5
dynamic to choose parallel when the physical write operation is synchronous
or sequential when the physical write operation is asynchronous.
■ Mirror Write Cache—Keeps a log of writes that are not yet mirrored, and uses
the log at recovery. Performance is slower during regular use to update the
log, but recovery time is faster.
Use when fast recovery of the data is essential. Turn off for mirrored swap
space that is also used as a dump. If this feature is on and the disk fails, the
dump will be erased.
■ Mirror Consistency—Makes all mirrors consistent at recovery. Recovery time
is slower. Performance is optimal during regular use.
Use for user data, or data that can be unavailable during a longer recovery.
Mirroring Root and Primary Swap
Root and swap logical volumes are defined during installation. You are prompted to
configure root disk mirroring during installation. If choose not to mirror the root
disk during installation, you can use either the mirror_on command or the
standard Logical Volume Manager (LVM) commands to do so after installation is
complete. The standard LVM procedure is described below.
When you mirror the root disk during installation, all logical volumes on the system
root disk, including primary swap, are mirrored on the physical volume that you
select as the mirror disk.
NOTE
Stratus recommends that you mirror the root logical volumes on two
disks that are dedicated to root data and that are on different SCSI buses.
Adding a Mirror to Root Data After Installation
After installation you can add a third mirror. To mirror a third disk, do the
following:
1. Create a bootable physical volume. To do this, enter
pvcreate -B /dev/rdsk/address
2. Add the physical volume to your existing root volume group. To do this, enter
vgextend /dev/vg00 /dev/dsk/address
3. Place boot utilities in the boot area. To do this, enter
mkboot /dev/rdsk/address