Mirror Disks in a Cluster

[Sharon Bi]

Dear all,

I am going to install one new disk to mirror another existing disk in a two node cluster. Could anybody tell me what is the proper procudure?

Thanks a lot and have a nice weekend!

Sharon

[Stefan Farrelly]

You havent said wether the disk you are adding is in a volume group which is in a serviceguard package. If not then all you need to do is pvcreate the new disk, add it to a vg, then extend the mirror.

If it is in a VG which is an SG package then it should also be relatively simply, all you need to do is ensure the VG definition on both nodes knows about the new disk;

Add the new disk to the VG you want to add it to, then on the primary node generate a map file of the volume group.

vgexport -p -s -m /tmp/vgXX.map /dev/vgXX

Copy this file to the other node in the cluster.

rcp /tmp/vgXX.map othernode:/tmp/vgXX.map

On the other node import the volume group definition.

vgimport -s -m /tmp/vgXX.map /dev/vgXX

On the other node activate the vg, mount the file system, check it, unmount
and deactivate the vg.

Now both nodes know about the disk. I think thats all you have to do.

[Rita C Workman]

May I interject a thought here...
Adding disks to a vg always results in the pkg concerned having to be stopped. In principle nothing has to be changed in the SG config, as long as NO new logical volumes are being created.
So to add disks to a SG environment you would need to do the following:
First stop the pkgs with the cmhaltpkg -v pkg_name
Do a cmviewcl -v to confirm they have stopped
Next remove the vg from the control of the cluster - vgchange -c n vg_ _
Activate the volume group - vgchange -a y vg _ _
******
At this point you can now make the changes to the vg by adding the disk and mirroring /sync'ng or whatever like you normally would.
When you have finished all your changes you need to put this vg backup under the control of the cluster.
*******
Deactivate the volume group - vgchange -a n vg _ _
Put the vol group back under cluster control - vg change -c y vg _ _

And remember that this command can only be done on an active cluster. If the entire cluster (cluster not pkg) is taken down it is best to reconfirm the configuration (using copy and apply), because the cluster will otherwise have problems activating the vol group concerned.

I think this is combination with the others info, may help you...
But remember to map out your plan first and take your time.....(and if you haven't gone for class on SG, I highly recommend you do...)
Regards,

[Sharon Bi]

/dev/dsk/c1t15d0 is already in the SG pkg. It is in vg05. Now, I am going to add a new disk, c2t15d0, to vg05, and make it a mirrorred copy of c1t15d0. And , I want this disk also in the cluster.

So, it that on the primary node, I do pvcreate, vgextend... and then vgexport to the secondary node and then vgimport. Do I have to modify any cmcluster conf file?

[Sharon Bi]

/dev/dsk/c1t15d0 is already in the SG pkg. It is in vg05. Now, I am going to add a new disk, c2t15d0, to vg05, and make it a mirrorred copy of c1t15d0. And , I want this disk also in the cluster.

So, it that on the primary node, I do pvcreate, vgextend... and then vgexport to the secondary node and then vgimport. Do I have to modify any cmcluster conf file?

[Stefan Farrelly]

no, as the cluster already knows about this VG you dont have to update any cluster config when adding a new disk to the VG.

[John Palmer]

Sharon,

Are you going to pysically install a new disk? If so you will have to run ioscan -fnC disk and insf -H on both servers to ensure that you have the disk device files.

You will also have to vgexport vg05 on the secondary server before you can do a fresh vgimport. This may involve removing it from the cluster first with vgchange -c n vg05. After vgimport you need to put it back in the cluster with vgchange -c y vg05.

Regards,
John