cloud foundation

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

Duncan Epping · Nov 10, 2025 · 4 Comments

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,

VMworld Reveals: VMware Cloud Foundation (#HBI1432BUR)

Duncan Epping · Sep 11, 2019 ·

At VMworld, various cool new technologies were previewed. In this series of articles, I will write about some of those previewed technologies. Unfortunately, I can’t cover them all as there are simply too many. This article is about VMware Cloud Foundation, which was session HBI1432BUR. For those who want to see the session, you can find it here. This session was presented by Mark Chuang and Jayanta K Dey. Please note that this is a summary of a session which is discussing the technology direction of the products, the discussed features may never be released, and this direction does not represent a commitment of any kind, and is subject to change. Now let’s dive into it, what is happening in the VMware Cloud Foundation space?

Jayanta kicked off with an introduction, and I believe most of you understand why we need to simplify IT, and if not, it is all about optimizing cost and improving speed/agility/time to market. This can only be achieved when you have a platform that caters for this, or basically a platform that enables you to focus on delivering services which are valuable to the business instead of focussing on the underlying infrastructure. This is where VMware Cloud Foundation comes in to play. It is a consistent and prescriptive full-stack hyperconverged infrastructure which can run any application.

VMworld Reveals: HCI Present and Futures (#HCI2733BU)

Duncan Epping · Sep 5, 2019 ·

At VMworld, various cool new technologies were previewed. In this series of articles, I will write about some of those previewed technologies. Unfortunately, I can’t cover them all as there are simply too many. This article is about HCI / vSAN futures, which was session HCI2733BU. For those who want to see the session, you can find it here. This session was presented by Srinivasan Murari and Vijay Ramachandran. Please note that this is a summary of a session which is discussing the roadmap of VMware’s HCI offering, these features may never be released, and this preview does not represent a commitment of any kind, and this feature (or it’s functionality) is subject to change. Now let’s dive into it, what is VMware planning for the future of HCI? Some of the features discussed during this session were also discussed last year, I wrote a summary here for those interested.

Vijay kicked off the session with an overview of the current state of HCI and more specifically VMware vSAN and Cloud Foundation. Some of the use cases were discussed, and it was clear that today the majority of VMware HCI solutions are running business-critical apps on top. More and more customers are looking to adopt full stack HCI as they need an end-to-end story that includes compute, networking, storage, security and business continuity for all applications running on top of it. As such VMware’s HCI solution has been focussed on lifecycle management and automation of all aspects of the SDDC. This is also the reason why VMware is currently the market leader in this space with over 20k customers and a market share of over 41%.