[ClusterLabs] Two-node cluster fencing

Casey & Gina Shobe caseyandgina at icloud.com
Sat May 12 14:51:05 EDT 2018

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,

> 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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