- Advertisement -
HomeStudy GuidesVCP-DCV for vSphere 7.xvSphere 7 - Describe ESXi Cluster Concepts

vSphere 7 - Describe ESXi Cluster Concepts

VMware vSphere 7.x Study Guide for VMware Certified Professional – Data Center Virtualization certification. This article covers Section 1: Architectures and Technologies. Objective 1.6 – Describe ESXi cluster concepts  

This article is part of the VMware vSphere 7.x - VCP-DCV Study Guide. Check out this page first for an introduction, disclaimer, and updates on the guide. The page also includes a collection of articles matching each objective of the official VCP-DCV.

Describe ESXi cluster concepts

Objective 1.6 is a parent of multiple key topics discussing vSphere clustering. Therefore, this article is a quick introduction and an overview of all the essential concepts to understanding ESXi clusters.

In VMware vSphere, there is no logic to talk about clusters without mentioning Distributed Resource Scheduler (DRS) and High Availability (HA); these are the two essential services that support the management of VMware clusters. However, we will discuss these concepts in the following topics. 

1. VMware Clustering

When I began studying VMware a couple of years ago, I had the same question that many in the virtualization realms had when the technology was just rising. What if a single server fails? Why put all your eggs (VMs) in one basket (Server)? It wouldn't be worth the benefits of saving computing resources by placing a couple of virtual servers into a physical one, as if this fails, you could lose all services. 

- Advertisement -

Due to this conception, for many, it was hard to flip the mental switch about the advantages of virtualization. People were still uncertain about virtualization, even though VMware included similar and even better clustering technologies than physical machines. These new virtual services delivered capabilities that previously required complex or expensive solutions to implement.

These services also provide significantly higher hardware utilization and better alignment of IT resources with business goals and priorities. In the past, companies have had to assemble a patchwork of the operating system or software application-specific solutions to obtain the same benefits. 

While using virtualization, even a powerful server can be overloaded with multiple computing tasks. To ensure better performance and reliability, we can use clustering technologies.

2. VMware Hosts and Clusters

Let's go back to the basics. 

2.1 ESXi Host

A Host represents the aggregate computing and memory resources of a physical server. For example, suppose the physical server has two 12-core CPUs running at 3.0 GHz each and 256 GB of system memory. In that case, the Host will have 72 GHz of computing power and 256 GBs of memory available for running virtual machines assigned to it. 

- Advertisement -

2.2 ESXi Cluster

A Cluster represents the aggregate computing and memory resources of a group of physical servers sharing the same network and storage arrays. For example, if the group contains four servers, each has two 12-core CPUs running at 3.0 GHz and 256 GB of memory. The Cluster will then have 288 GHz of computing power and 1,024 GB of memory available for the running virtual machines assigned to it. 

 

VMware Hosts and Clusters

Admins (the virtual resource owners) do not need to be concerned with the physical composition (number servers, quantity, and type of CPUs) of the underlying cluster to provision resources. Admins set up the resource provisioning policies based on the aggregate available resource. vSphere will automatically assign the appropriate resources dynamically to the virtual machines within the boundaries of those policies.

2.3 Resource Pools

Resource pools simplify control over the resources. They provide a flexible and dynamic way to divide and organize computing and memory resources from a Host or a Cluster. vSphere virtualizes and aggregates industry-standard servers (processors, memory, their attached network, and storage capacity) into logical resource pools (from a single ESX Server host or a VMware cluster) that can be allocated to virtual machines on demand. Any Resource Pools can be partitioned into smaller Resource Pools at a fine-grain level to divide further and assign resources to different groups or for various purposes.

3. VMware DRS and HA

In general, the two essential services that support the management of VMware clusters are VMware DRS and HA. 

VMware DRS provides automatic initial virtual machine placement and makes automatic resource relocation and optimization decisions as hosts are added or removed from the cluster or the load on individual virtual machines changes. 

Now, suppose an ESXi host goes offline. It will take down all virtual machines running on that single host. VMs won't come back online until you restore the server or restore them to another server using a backup and restore process. These processes can be very time‑consuming. VMware HA allows these virtual machines running on the host to be switched over to use other host resources in the cluster in the case of host machine failures. 

More about these topics and concepts in following vSphere 7 objectives.

Resources

Understanding Clones in VMware vSphere 7

Horizon 7 Architecture Planning

- Advertisement -

Conclusion

The topic reviewed in this article is part of the VMware vSphere 7.x Exam (2V0-21.20), which leads to the VMware Certified Professional – Data Center Virtualization 2021 certification. 

Section 1 - Architectures and Technologies. 

Objective 1.6 – Describe ESXi cluster concepts 

See the full exam preparation guide and all exam sections from VMware.

More topics related to VMware

Juan Mulford
Juan Mulford
I have been active in IT for over fourteen years now. I am a solutions architect, working with storage, virtualization, and VDI solutions. For the past ten years, I have been living and working in Taiwan.

Leave a Reply

- Advertisement -

Popular Articles

mulcas.com-Raspberry-Pi

Raspberry Pi OS in a Virtual Machine with VMware

4
Although the Raspberry Pi OS is designed and optimized for the Raspberry Pi module, it is possible to test and use it without its hardware, with VMware. This solution can be useful if you are a developer (or just a curious guy) and don't have a Raspberry Pi module with you
Unable to delete inaccessible datastore

Unable to delete an "inaccessible" datastore

7
I was switching my storage array, so I migrated the VMs from that old datastore/storage to a new datastore/storage. The old datastore was shared by 3 ESXi hosts, no cluster. After migrating the VMs and unmount/delete the datastore, it was still presented in two of the ESXi hosts and was marked as inaccessible.
This is not a valid source path / URL

This is not a valid source path / URL - SourceTree and Gitlab

0
I have been working on a project with a friend who set up a repository in Gitlab but even though I was able to view all projects on it, I couldn’t really join the repository. I was using SourceTree and Gitlab.
mulcas.com-VMware-OVF-Tool

How to export a Virtual Machine using the VMware OVF Tool

9
The VMware OVF Tool is implemented by VMware for easily importing and exporting virtual machines in Open Virtualization Format (OVF) standard format. Here, I want to show you how to download and install it, and then how to use it from a Windows machine.
Couldn't load private key - Putty key format too new

Couldn't load private key - Putty key format too new

5
couldn't load private key - Putty key format too new.” This issue happens when you use PuTTygen to generate or convert to a ppk key. Here is how to fix it. 
- Advertisement -

Recent Comments