Yellow Bricks

by Duncan Epping

vsan

Does a Site Takeover work with a 2-node configuration?

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I got a question last week if vSAN Site Takeover also works with a 2-node configuration, and my answer was: yes, it should work. However, I had never tested it, so I figured I would build a quick lab environment and see if I was right. I recorded the result, here it is! The demo is pretty straight forward, let me describe what you will see:

  • 2-node vSAN environment
  • 1 VM named “photon-001”
  • Photon-001 VM is “stretched” across both hosts and has a witness component on the witness host
  • Host “.245” and the witness will fail and the components on those hosts will go “absent”
  • Photon-001 VM becomes inaccessible
  • We run the site-takeover command, which will reconfigure the Photon-001 VM
  • The Photon-001 VM becomes available again and it automatically restarted

#108 – My Explore recap: VCF Native S3 Object Storage, Cyber Recovery, and vSAN on FC!

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I had some difficulties scheduling guests the past weeks due to my travel schedule, and as a result, I figured I would try something new. In this episode, I go over the various things I announced at Explore and Explore on Tour in London, Paris, and Frankfurt. I talk about VCF Native S3 Object Storage, the enhancements we are planning for Disaster Recovery as well as Cyber Recovery, and I also briefly touch on vSAN on FC.

You can listen to my solo episode, episode 108, on Spotify (bit.ly/3MxRyZC), Apple Podcasts (bit.ly/4iEM5ML), or via the embedded player on Yellow-Bricks below.

If you like to hear more about vSAN ESA Global Deduplication, make sure ⁠to go to this blog on Yellow-Bricks⁠, as it contains the links to the discussion Pete Koehler and I had on the show a while back. I also just published the demo I recorded for Explore on Youtube, make sure to watch that one!

I also had Jatin Jindal on the show a month or two ago to discuss all Ransomware/Cyber Recovery enhancements in-depth. You can listen to that episode via Spotify (bit.ly/3IWQCwz), Apple (bit.ly/4o6YVoG), or via the embedded player on yellow-bricks.com!

vSAN 9.0 Site Maintenance Mode demo!

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I had a few questions about this, so I figured I would record a quick demo showing Site Maintenance. In the demo, I have a stretched cluster configured in vSAN 9.0, and I am going to place the Preferred Site into maintenance mode. First a pre-check will occur to verify all workloads are replicated between locations, and then the site is placed into maintenance while maintaining data consistency across hosts. Next demo I will record will show the Manual Site Takeover command that was also introduced in 9.0 for OSA, but will be also available soon for ESA.

What do I do after a vSAN Stretched Cluster Site Takeover?

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Over the last couple of months, various new vSAN features were announced. Two of those features are around the Stretched Cluster configuration, and have probably been the number 1 feature request for a few years. Now that we have Site Takeover and Site Maintenance functionality available, I am starting to get some questions about the impact of them, and in particular, the Site Takeover functionality is raising some questions.

For those who don’t know what these features are, let me describe them briefly:

Site Maintenance = The ability to place a full vSAN stretched cluster Fault Domain into maintenance mode at once. This ensures that all hosts within the fault domain have consistently stored the data, and all hosts will go into maintenance mode at the same time.

Site Takeover = This provides the ability when a Witness and a Data Site has failed to bring back the remaining site through a command line interface. This will reconstruct the remaining “site local” RAID configuration, making the objects available again, which will then allow vSphere HA to restart the VMs.

Now, the question that the above typically raises is what happens to the Witness and the Data Site that failed when you do the Site Takeover? If you look at the VMs RAID configuration, you will notice that both the Witness and the Data Site components of the sites that failed will completely disappear from the RAID configuration.

But what do you do next, because even after you run the Site Takeover, you still see your hosts and the witness in vCenter Server, and you still see a stretched cluster configuration in the UI. Now at first I thought that if the environment was completely up and running again, you had to go through some manual effort to reconstruct the stretched cluster. Basically, remove the failed hosts, wipe the disks, and recreate the stretched cluster. This is, however, not the case.

In the example above, if the Preferred site and the Witness site return for duty, vSAN will automatically discard the stale components in those previously failed sites. It will recreate new components for all objects, and it will do a full resync of the data.

If you end up in a situation where your hosts are completely gone (let’s say as a result of a fire), then you will have to do some kind of manual cleanup as follows, before you rebuild and add hosts back:

  • Remove the failed hosts from the vCenter inventory
  • Remove the witness from the vCenter inventory
    • Delete the witness from the vCenter Server it is running, a real delete!
  • Delete the surviving Fault Domain, this should be the only Fault Domain still listed in the vCenter interface
  • You now have a normal cluster again
  • Rebuild hosts and recreate the stretched cluster

I hope that helps,