ESXi

Hey guys!

I have 4 independent ESXi servers running 6.7 and 7.0 respectively managed by a vCenter 7. Right now the servers are not joined in any type of clusters, etc.

Is there a good tutorial around on how to create a cluster with hosts already running production VMs in order to join them and get the benefits of having them inside the cluster?

What would be the best approach? most of my servers are SQL server running machines, so what would be the best way to go about making this transition from independent hosts managed by a vCenter to joining all 4 hosts into a cluster to better manage resources?

Since the environment has been like this for years I want to make sure I go the right way about this.

All servers have the same processor/memory and SSD drives so they are identical.

Thanks so much in advance.

Teo

I'm not sure about a tutorial, however I'm sure someone in the community has a link to one.  

Personally, I would vmotion VMs off of the 6.7 host(s) [one at a time if there are more than one], and upgrade that/those to 7.x if you have the licensing.  Once all the hosts are at the same version,  I would start building a cluster of two (without VMs) and then migrate VMs to those, and then add the 'empty' hosts to the cluster, and then use DRS to re-distribute the VMs accordingly.

Not an easy or fast process by any means, but that is how I would approach it. 

Are the independent hosts all similar in chipset/memory/storage resources?  Not a big deal if they are not, but that is also a consideration. 

Besides taking advantage of cluster resource usage, is there another reason to undertake this reconfiguration?

It's generally not recommended to mix different versions of ESXi hosts within the same cluster. While it might be technically possible to add ESXi hosts with different versions (like 6.7 and 7.0 in your case) to the same cluster, it can lead to compatibility issues and might limit the functionality of features like vMotion and DRS (Distributed Resource Scheduler).

For best practices and optimal cluster performance, it's advised to standardize the ESXi host versions within a cluster. Upgrading all hosts to the same version before forming a cluster is usually the recommended approach. This ensures compatibility and allows you to fully leverage the capabilities of vCenter and cluster features.

then 

Pre-cluster configuration:

• Update VMware Tools on all VMs to ensure compatibility.
• Configure identical networking on all hosts.
• Configure and present shared storage to all hosts.

for SQL Servers

• Choose times of low production activity for migrations.
• Utilize vMotion for live migration with minimal disruption.
•  Configure HA for SQL servers to ensure failover in case of host failures.
• Utilize shared storage (SAN or vSAN) for high availability and performance.
• Consider clustering SQL Server instances for additional high availability and scalability.

for a start, the following is the official doc from VMware 

https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.vcenterhost.doc/GUID-32E79431-7DC9-48DB-A72C-CCA652A3B588.html

https://docs.vmware.com/en/VMware-vSphere/8.0/vsphere-vcenter-esxi-management/GUID-F7818000-26E3-4E2A-93D2-FCDCE7114508.html