Using Serviceguard Extension for RAC, 8th Edition, March 2009

disks you have defined on the array. If you are using SAM, choose the type of disk array you
wish to configure, and follow the menus to define alternate links. If you are using LVM commands,
specify the links on the command line.
The following example shows how to configure alternate links using LVM commands. The
following disk configuration is assumed:
8/0.15.0 /dev/dsk/c0t15d0 /* I/O Channel 0 (8/0) SCSI address 15 LUN 0 */
8/0.15.1 /dev/dsk/c0t15d1 /* I/O Channel 0 (8/0) SCSI address 15 LUN 1 */
8/0.15.2 /dev/dsk/c0t15d2 /* I/O Channel 0 (8/0) SCSI address 15 LUN 2 */
8/0.15.3 /dev/dsk/c0t15d3 /* I/O Channel 0 (8/0) SCSI address 15 LUN 3 */
8/0.15.4 /dev/dsk/c0t15d4 /* I/O Channel 0 (8/0) SCSI address 15 LUN 4 */
8/0.15.5 /dev/dsk/c0t15d5 /* I/O Channel 0 (8/0) SCSI address 15 LUN 5 */
10/0.3.0 /dev/dsk/c1t3d0 /* I/O Channel 1 (10/0) SCSI address 3 LUN 0 */
10/0.3.1 /dev/dsk/c1t3d1 /* I/O Channel 1 (10/0) SCSI address 3 LUN 1 */
10/0.3.2 /dev/dsk/c1t3d2 /* I/O Channel 1 (10/0) SCSI address 3 LUN 2 */
10/0.3.3 /dev/dsk/c1t3d3 /* I/O Channel 1 (10/0) SCSI address 3 LUN 3 */
10/0.3.4 /dev/dsk/c1t3d4 /* I/O Channel 1 (10/0) SCSI address 3 LUN 4 */
10/0.3.5 /dev/dsk/c1t3d5 /* I/O Channel 1 (10/0) SCSI address 3 LUN 5 */
Assume that the disk array has been configured, and that both the following device files appear
for the same LUN (logical disk) when you run the ioscan command:
/dev/dsk/c0t15d0
/dev/dsk/c1t3d0
Use the following procedure to configure a volume group for this logical disk:
1. First, set up the group directory for vg_ops:
# mkdir /dev/vg_ops
2. Next, create a control file named group in the directory /dev/vg_ops, as follows:
# mknod /dev/vg_ops/group c 64 0xhh0000
The major number is always 64, and the hexadecimal minor number has the form
0xhh0000
where hh must be unique to the volume group you are creating. Use the next hexadecimal
number that is available on your system, after the volume groups that are already configured.
Use the following command to display a list of existing volume groups:
# ls -l /dev/*/group
3. Use the pvcreate command on one of the device files associated with the LUN to define
the LUN to LVM as a physical volume.
# pvcreate -f /dev/rdsk/c0t15d0
It is only necessary to do this with one of the device file names for the LUN. The -f option
is only necessary if the physical volume was previously used in some other volume group.
4. Use the following to create the volume group with the two links:
# vgcreate /dev/vg_ops /dev/dsk/c0t15d0 /dev/dsk/c1t3d0
LVM will now recognize the I/O channel represented by/dev/dsk/c0t15d0 as the primary
link to the disk; if the primary link fails, LVM will automatically switch to the alternate I/O
channel represented by /dev/dsk/c1t3d0. Use the vgextend command to add additional
disks to the volume group, specifying the appropriate physical volume name for each PV link.
Repeat the entire procedure for each distinct volume group you wish to create. For ease of system
administration, you may wish to use different volume groups to separate logs from data and
control files.
Creating a Storage Infrastructure with LVM 45