[ClusterLabs] Two-node cluster fencing

[Confidential Company]

Hi Casey,

1. I tried shutting down my VM while testing, the "ClusterIP" resource
switched automatically onto the standy node(Node2)
2. I do "systemctl enable corosnyc/pacemaker" - so that after reboot,
corosync and pacemaker will automatically start.
3. As I turn-on Node1, I experienced downtime (maybe syncing of nodes will
result of downtime), but my cluster still works as expected --> The active
node is still Node2.
4. If I choose ESXI as my fence device, if the physical server goes down,
would it still be reasonable because its on one host?


Thanks Casey, I want to understand more about fencing.


Regards,

imnotarobot










>>Without fencing, if the primary is powered off abruptly (e.g. if one of
your ESX servers crashes), the standby will not become primary, and you
will need to promote it manually.  We had exactly this scenario happen last
week with a 2-node cluster.  Without fencing, you don't have high
availability.  If you don't need high availability, you probably don't need
pacemaker.

There are instructions for setting up fencing with vmware here:
https://www.hastexo.com/resources/hints-and-kinks/fencing-vmware-virtualized-pacemaker-nodes/

One note - rather than the SDK, I believe you actually need the CLI
package, which can be found here:
https://my.vmware.com/web/vmware/details?downloadGroup=VCLI600&productId=491

Good luck - I haven't managed to get it to build yet - vmware gives you a
black box installer script that compiles a bunch of dependent perl modules,
and it ends up getting hung with 100% CPU usage for days - digging into
this further with lsof and friends, it seems to be prompting for where your
apache source code is to compile mod_perl.  Why does it need mod_perl for
the CLI??  Anyways, I haven't managed to get past that roadblock yet.  I'm
using Ubuntu 16 so it may happen to just work better on your RHEL
instances.  If you have a different ESX version than 6.0, you may have
better luck as well.

Best wishes,
-- 
Casey

> On May 11, 2018, at 10:31 PM, Confidential Company <sgurovosa at gmail.com>
wrote:
>
> Hi,
>
> This is my setup:
>
> 1. I have Two vMware-ESXI hosts with one virtual machine (RHEL 7.4) on
each.
> 2. On my physical machine, I have four vmnic --> vmnic 0,1 for uplink
going to switchA and switchB --> vmnic 2,3 for heartbeat corosync traffic
(direct connect to other ESXI host)
> 3. I plan on clustering my two virtual machines via corosync and create a
virtual-IP via pacemaker.
> 4. I plan on using the uplink interface for data and totem interface for
corosync packets(heartbeat messages).
> 5. These two virtual machines doesnt need for a shared storage, or a
shared LUN because the application is, by nature, a standalone application
that doesnt need to have a centralized location as it does not store any
data that needs to be synchronized between two servers.
> 6. I have a PC that only needs to contact the Virtual IP of the rhel
virtual servers.
> 7. Seamless failover from primary to secondary is not required.
> 8. Active/Passive setup
>
>
> Given the setup above,
> 1. Is there any drawbacks?
> 2. Do I need fencing? Can you explain me by giving a scenario on the
above setup? What instances will occur if I didnt put a fence device?
> 3. If I need a fence device? what fence device you recommend? SAN,
vmWare, or PDU?
>
>
> Thanks,
>
> imnotarobot
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