What is vSphere High Availability (HA) and DRS Compared

What is vSphere High Availability

Virtualization has certainly changed the way many enterprises organize their business. When virtual machines are running, it is essential to ensure the availability of them during the business hours. Therefore, VMware provide the clustering feature to ensure high availability.

VMware vSphere High Availability (HA) is a utility included in vSphere suite that provides high availability for virtual machines. It pools the virtual machines and the hosts they reside on into a cluster for monitoring, automatically restart failed virtual machines on alternative host servers to reduce application downtime.

VMware first introduced vSphere HA in Virtual Infrastructure 3 in 2006 and has continued to develop and support the feature. So far vSphere has provided essential failover protection for many enterprises. Next, this article will give you an overview of how vSphere HA works and its specific features.

How vSphere High Availability works

vSphere HA uses a utility called the Fault Domain Manager agent to monitor ESXi host availability and to restart failed VMs. When configuring vSphere HA, you define a group of servers as a HA cluster, and the Fault Domain Manager runs on each host within the cluster.

A single host is automatically elected as the primary host. The primary host communicates with vCenter Server and monitors the state of all protected virtual machines and of the secondary hosts.

Different types of host failures are possible, and the primary host uses network and datastore heartbeating, a periodic message that indicates the host is running status, to determine the type of failure. After that, the primary host must distinguish between a failed host and one that is in a network partition or that has become network isolated, and appropriately deal with the failure.

In the case of a VM failure in which the host server continues to run, vSphere HA restarts the VM on the original host. If an entire host fails, the utility restarts all affected VMs on other hosts in the cluster.

Compare the Differences: vSphere HA vs DRS

vSphere High Availability (HA) and Distributed Resource Scheduler (DRS) are two essential features in VMware's vSphere environment, each serving distinct purposes in ensuring the reliability and efficiency of virtualized resources.

1. Purpose

• vSphere HA: This feature is designed to provide high availability for virtual machines (VMs). In the event of a host failure, HA automatically restarts VMs on other available hosts in the cluster, minimizing downtime and ensuring business continuity.

• DRS: DRS optimizes resource allocation across hosts in a cluster. It automatically balances workloads by migrating VMs between hosts based on resource usage, ensuring efficient utilization of CPU and memory.

2. Functionality

• vSphere HA: HA operates by monitoring the hosts in a cluster. If a host becomes unresponsive, HA triggers a restart of the VMs on a different host. It does not require VMotion or any network configuration.

• DRS: DRS uses real-time resource monitoring to make decisions about VM placement and migration. It employs vMotion technology to live migrate VMs without downtime, based on pre-defined rules and resource utilization.

3. Configuration

• vSphere HA: Configuration involves setting up a HA cluster, enabling HA for the cluster, and defining failover settings. It is primarily focused on availability rather than resource management.

• DRS: DRS requires the creation of a DRS cluster and involves setting resource pools, affinity rules, and migration thresholds. It focuses on performance and resource optimization.

4. Use Cases

• vSphere HA: Ideal for organizations that prioritize uptime and need a failover solution for critical applications. It ensures that VMs are quickly restarted after host failures.

• DRS: Best suited for environments with variable workloads that need efficient resource management. It helps maintain performance and prevent resource bottlenecks by dynamically balancing workloads.

Create vSphere backup to protect critical VMs from accidental loss

vSphere High Availability can recover the business running on virtual machines in time to reduce downtime. However, even the perfect cluster configuration cannot completely prevent unexpected data loss. With vSphere 6.5 become the last release that includes vSphere Data Protection, VMware has decided to exit the data protection market and focus its investments on VMware vSphere Storage APIs.

That means you may need to migrate your backup policies to other third-party software. If you still haven’t chosen one, here I introduce you to a VMware backup software AOMEI Cyber Backup, it enables you to backup multiple VMs in VMware vSphere within 3 simple steps. And it offers you the following benefits:

✦ Agentless Backup: create complete and independent image-level backup for VMware ESXi and Hyper-V VMs.
✦ Support Free ESXi: AOMEI Cyber Backup support both paid and free versions of VMware ESXi.
✦ Flexible vSphere Backup: backup large numbers of VMs managed by vCenter Server, or multiple VMs on standalone ESXi host.
✦ Automated Execution: schedule to automate backups daily, weekly, and monthly with email notifications.
✦ Role Assignment: allows one administrator to create sub-accounts with limited privileges.

AOMEI Cyber Backup supports VMware vSphere/ESXi 6.0 and later versions. And simplifies the process of backing up VMs into 3 simple steps. Next, I will show you how to backup multiple VMware ESXi VMs via AOMEI Cyber Backup. You can click the following button to download the free trial.

*You can choose to install this VM backup software on either Windows or Linux system.

Simple steps to create a vSphere backup task

Step 1. Bind Devices: Access to AOMEI Cyber Backup web client, navigate to Source Device > VMware > + Add VMware Device to Add vCenter or Standalone ESXi. And then click … > Bind Device.

Step 2. Create Backup Task: Navigate to Backup Task > + Create New Task, select the Device Type as VMware ESXi Backup, then you can configure the backup task as following.

• Device: select multiple VMs from added vCenter Server or standalone ESXi host.
• Target: back up to a local path, or to a network path such as NAS.
• Archive : select the added S3 bucket to archive backup versions to Amazon S3.
• Schedule: choose to perform full, differential or incremental backup, and automate execution according to the frequency you specified.
• Backup cleanup: configure a retention policy to auto delete old backup files and save storage space.

Step 3. Run Backup: Click Start Backup and select Add the schedule and start backup now, or Add the schedule only.

Step 4. Click Restore to perform fast recovery when the original VM corrupted. When restoring, you can also restore to new location to create a new VM in the same or another datastore/host directly from the backup, saves the trouble of re-configuring the new VM.

Summary

If you are looking for a way to failover and reduce downtime, then vSphere High Availability may be just what you need. In this article, I briefly introduced what is vSphere High Availability, how vSphere HA works, and its specific features.

Except for High Availability, vSphere also provide Fault Tolerance (FT) and Redundancy for you to build a 24/7 IT infrastructure and disaster recovery plan. Check more details in High Availability vs Fault Tolerance vs Redundancy.