Tag Archives: mixed cluster

Migrating Oracle RAC from SuSE to OEL (or RHEL) live

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I have a customer that needs to migrate its Oracle RAC cluster from SuSE to OEL.

I know, I know, there is a paper from Dell and Oracle named:

How Dell Migrated from SUSE Linux to Oracle Linux

That explains how Dell migrated its many RAC clusters from SuSE to OEL. The problem is that they used a different strategy:

– backup the configuration of the nodes
– then for each node, one at time
– stop the node
– reinstall the OS
– restore the configuration and the Oracle binaries
– relink
– restart

What I want to achieve instead is:
– add one OEL node to the SuSE cluster as new node
– remove one SuSE node from the now-mixed cluster
– install/restore/relink the RDBMS software (RAC) on the new node
– move the RAC instances to the new node (taking care to NOT run more than the number of licensed nodes/CPUs at any time)
– repeat (for the remaining nodes)

because the customer will also migrate to new hardware.

In order to test this migration path, I’ve set up a SINGLE NODE cluster (if it works for one node, it will for two or more).

I have to setup the new node addition carefully, mainly as I would do with a traditional node addition:

  • Add new ip addresses (public, private, vip) to the DNS/hosts
  • Install the new OEL server
  • Keep the same user and groups (uid, gid, etc)
  • Verify the network connectivity and setup SSH equivalence
  • Check that the multicast connection is ok
  • Add the storage, configure persistent naming (udev) and verify that the disks (major, minor, names) are the very same
  • The network cards also must be the very same

Once the new host ready, the cluvfy stage -pre nodeadd will likely fail due to

  • Kernel release mismatch
  • Package mismatch

Here’s an example of output:

So the problem is not if the check succeed or not (it will not), but what fails.

Solving all the problems not related to the difference SuSE-OEL is crucial, because the addNode.sh will fail with the same errors.  I need to run it using -ignorePrereqs and -ignoreSysPrereqs switches. Let’s see how it works:

Then, as stated by the addNode.sh, I run the root.sh and I expect it to work:

Bingo! Let’s check if everything is up and running:

So yes, it works, but remember that it’s not a supported long-term configuration.

In my case I expect to migrate the whole cluster from SLES to OEL in one day.

NOTE: using OEL6 as new target is easy because the interface names do not change. The new OEL7 interface naming changes, if you need to migrate without cluster downtime you need to setup the new OEL7 nodes following this post: http://ask.xmodulo.com/change-network-interface-name-centos7.html

Otherwise, you need to configure a new interface name for the cluster with oifcfg.

HTH

—

Ludovico