HP Serviceguard Extended Distance Cluster for Linux A.12.00.00 Deployment Guide, March 2014

3.3.3.1 Creating and Assembling an MD Device
This example shows how to create the MD device /dev/md0, you must create it from a LUN of
storage device 1 (/dev/hpdev/sde ) and another LUN from storage 2 (/dev/hpdev/sdf ) .
To create an MD device:
1. Run the following command:
# mdadm --create --verbose /dev/md0 --name=0 --level=1
--raid-devices=2 /dev/hpdev/sde /dev/hpdev/sdf
2. To have the name of MD device consistent across the nodes, copy the output of # mdadm
–Db /dev/md0 command to /etc/mdadm.conf file:
mdadm –Db /dev/md0
The output will be as follows:
ARRAY /dev/md0 metadata=1.2 name=node1.ind.hp.com:0
UUID=354b6919:e7db657c:1864a2c0:481b5f36
NOTE: Ensure that you copy the output to /etc/mdadm.conf file for each node.
Once the new RAID device, /dev/md0, is created on one of the cluster nodes, you must assemble
it on the nodes where the package must run.
To enable write intent internal bitmap on MD device, see “Enabling and Disabling Write Intent
Internal Bitmap” (page 52).
NOTE: Use of write intent internal bitmap is supported on the following patches and later:
• SGLX_00455 on Red Hat Enterprise Linux 5
• SGLX_00456 on Red Hat Enterprise Linux 6
• SGLX_00457 on SUSE Linux Enterprise Server 11
You create an MD device only once and you can manage other functions using the serviceguard-xdc
scripts.
To assemble the MD device, complete the following procedure:
1. Stop the MD device on the node where you created it, by running the following command:
# mdadm -S /dev/md0
2. On the other nodes, do the following:
a. Run the following command:
# mdadm -A -R /dev/md0 /dev/hpdev/sde /dev/hpdev/sdf
b. To have the name of MD device consistent across the nodes, see step 2 as described in
creating MD device.
3. Stop the MD device on the other node by running the following command:
# mdadm -S /dev/md0
You must stop the MD device soon after you assemble it on the second node.
4. If you want to create volume groups, restart the MD device on the first node by running the
following command:
# mdadm -A -R /dev/md0 /dev/hpdev/sde /dev/hpdev/sdf
5. After you have created the volume groups, stop the MD device by running the following
command:
# mdadm -S /dev/md0
24 Configuring your Environment for Software RAID