Installation guide

Setting Up I/O Channel Separation
4-8 Fault Tolerant System Administration (R1004H) HP-UX version 11.00.03
Setting Up I/O Channel Separation
Stratus recommends that you use I/O channel separation for the physical volumes
within a volume group to maintain logical volume mirroring across different SCSI
buses. Doing this is important because if a site does not set up I/O separation, the
site could perform strict mirroring but still not be fully duplexed, as the mirroring
could occur on two different physical volumes but on the same SCSI bus.
To set up I/O channel separation, the following conditions must exist:
■ at least two physical volume groups must be defined within each volume
group
■ each physical volume group must contain two or more physical volumes
(disks) that share a SCSI bus
■ each physical volume group within a volume group must contain disks with
the same total amount of storage space.
■ each logical volume in the volume group must be mirrored using separate
physical volume groups
The following example shows how to set up I/O separation for a set of four disks
using two SCSI buses.
1. Create the physical volumes. To do this, enter
pvcreate /dev/rdsk/c0t2d0
pvcreate /dev/rdsk/c0t3d0
pvcreate /dev/rdsk/c1t2d0
pvcreate /dev/rdsk/c1t3d0
These statements inform LVM that it can use the four physical volumes, or
disks, mounted to the device addresses specified.
2. Create the volume group vgdata. To do this, enter
mkdir /dev/vgdata
mknod /dev/vgdata/group c 64 0x010000
These statements create the vgdata volume group in an empty state.
3. Create a physical volume group named lsb0 that contains two of the physical
volumes defined in step 1 to the volume group. To do this, enter
vgcreate -g lsb0 vgdata /dev/dsk/c0t2d0 /dev/dsk/c0t3d0
This statement initializes the volume group vgdata with the physical volume
group lsb0, which contains two disks on logical SCSI bus 0, c0t2d0 and
c0t3d0.