learning experiments on gfs2 clustering: no-quorum-policy,interleave, ordered

It has been probably a week of gfs2 (global filesystem, 2) crash course in my personal study on clustered filesystems.   Here is an in depth experiment result on 3 detail points that is mentioned in the RedHat manual:

Point 1: set no-quorum-policy to freeze
Point 2: when creating dlm and clvmd clones, set interleave=true
Point 3: when creating dlm and clvmd clones, set ordered=true

Experiments and explanations:

Point 1: What does "no-quorum-policy=freeze" do?

To differentiate a "freeze" with something else, a gfs2 cluster filesystem is tested with the following two options:

pcs property set no-quorum-policy=stop
pcs property set no-quorum-policy=freeze

With "stop", the resources are stopped, resulting in the gfs2 filesystems being unmounted (because the filesystems are just services).

With "freeze", I/O is blocked, until the problem is corrected.  Specifically, commands like this are frozen:

   ls > /path/to/gfs2/filesystem/sample-output.txt

When the problem gets fixed and the cluster becomes quorate again, the command resumes normally.

Point 2: interleave=true

This is the parameter that caused me much grief for a day or so.  When I had my first sucessful gfs2 clustered filesystem configured i was dissapointed that the filesystems were being unmounted when the nodes re-enter the cluster.  I found the answer by searching the web:  ALL instances dlm or/and clvmd clones need to restart before ANY gfs mount, when interleave = false. 

So basically if resource2 clone is dependent on resource1 clone, and interleave=false, then ALL instances of resource1 has to be present before ANY instance of resource1.  This results in the gfs2 filesystems being unmounted and re-mounted (in our example, where resource1 is the gfs2 mounts).

Thank you for the person who posted it, which I found on google.

Point 3: ordered=true

I have no observable difference to report, seems to make no difference either way.  I have tested this to true and false and the lm/clvm processes seem to start the same way on all nodes.

JondZ 201603