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Splitting large CFS cluster

Created: 09 Mar 2011 • Updated: 28 Mar 2011 | 2 comments
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I've been tasked with splitting are large CFS cluster (SLES11/SFS 5.1), no application service groups thankfully, just CFS sg's... I've identified where the splits can be made and the first task will be to take 2 nodes out of the large cluster and create a seperate cluster from them.

The question I have is whats the recommended way to remove nodes from the cluster. I'm happy with doing the gab/llt part.

Most docs state using the 'hagrp -modify' on cvm group for AutoStartList/SystemList, also cvm_clus for CVMNodeID and CFSMount / NodeList + hasys -delete etc..

However looking at the 'cfsmntadm/cfsdgadm delete' commands, they appear to do all the work instead ?

Not having a play cluster to test on I'd rather get some heads up from anyone who knows this for sure.


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Gaurav Sangamnerkar's picture


You are right ... most of the docs state the traditional way of doing the stuff using ha commands however technically yes, cfs commands should be able to do the task for you.. (removing groups from configuration)

From man page for cfsmntadm delete:

          Deletes the cluster mount instance by dissociating  the
          shared  volume  (cluster  file  system)  from the mount
          point on various nodes.  cfsmntadm delete also  removes
          the  definition  of  a  cluster mount instance from the
          cluster configuration  that  was  previously  added  by
          cfsmntadm  add.   After a cluster mount is deleted, the
          shared volume cannot be mounted by  the  cfsmount  com-
          mand.   Deleting  a  mount  instance  can fail if it is
          mounted, or if it is the parent of a Storage Checkpoint
          or snapshot mount instance.

For cfsdgadm delete:

 delete    Removes the shared disk group from the cluster  by
               disassociating  it  from the nodes in the cluster.
               This option deletes  the  information  related  to
               this shared disk group from the cluster configura-
               tion.  After the shared disk group  is  disassoci-
               ated  from  the  nodes  in the cluster, the shared
               disk group is not automatically activated when the
               node joins the cluster.

               Note:  The delete will fail if any  shared  volume
               belonging to this disk group is currently mounted.
               If the -f option is  specified,  the  volumes  are
               unmounted and the delete process continues.

It clearly states what it would be doing. As you mentioned that you have only CFS groups then for sure this should remove the CFS group definitions from for you however CFS commands won't be making changes to llttab / gabtab / vxfenmode / llthosts for you since they are lying at the lower layer. These will need to be modified manually which you said you would be ok with..


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guyvert1's picture


Thanks for your thoughts, I did have a look through the lib scripts for these commands, although its pretty hard to fully track the functions they do appear to do all the leg work on .

I'll tread carefully when I do the work and update this thread with findings