In this video, Russ Long dives into some of the basic features of High Availability (HA). Study the different features of HA, and what problems they help solve.
- [Narrator] Okay so the purpose of HA is to allow us an automatic response when a host fails. This is really important because when a host fails we are left out in the cold, aren't we? There's nothing we can do, we lose multiple VMs. When a host fails with HA in place, we have the VMs migrate from that failed host to another host in the cluster. Now to implement HA all you need is a Standard, Enterprise or Enterprise Plus license. Now I know what some of you just thought, that's all the licensing, and that's correct, it's available across all licensing for VMware.
Now it's also centrally managed through vCenter Server, so as long as you have a vCenter Server, or the vCenter Server appliance in your environment you'll be able to control HA. So let's dive into a little bit of the details of HA. HA can detect other types of failures. Not just failures for the host, but actually for the VM and application as well. Now I'm going to put a little star next to that. It's not every application. The application must have an API for it.
So if you have a Vmware approved, a pre approved application, it'll work just fine. But if you're in a large company that creates custom applications, you're going to need to create that API for yourself. And last but not least, configuration dependent for these other types of failures. We're actually going to mess with some custom configurations to determine just how we're going to detect these failures. HA is dependent on many technologies with the Vsphere world, so its performance is tied to performance of other major categories within our Vsphere environment.
The first is migration. If we can live migrate virtual machines within our cluster without a problem, then your HA performance in that particular area is going to do well. Now if we have trouble or we're struggling to do migration or maybe we have a cluster with different vendor CPUs on either side of it, we're going to have a major problem with migration. So you can see how migration can affect HA performance. Now storage performance is also critical in the functioning of HA.
Storage performance determines how fast we can access those files that are located on our shared storage appliance, our IOPs, our reads and writes, those are incredibly important. Remember when a host fails, how we recover a virtual machine is by accessing those virtual machine files that are located on storage. So the quicker we can access them, the quicker we can begin the migration to another host in the cluster. That brings up my next point. Our cluster has to work. We just have to have good communication within our cluster.
We have to have hosts that are very similar within our cluster. Overall cluster performance has to be dialed in in order to get the most out of HA. Last but not least, and one of the most important things for HA is our network performance. Remember we have communication that takes place between these hosts that determine if they're up or down. That's how we know if there's a failure, through network communication. If my network is sluggish or high latency I can see false positives, which can cause big problems for HA.
Note: This course will also help you prepare for the Configure and Administer vSphere Availability Solutions domain of the VMware Certified Professional – Data Center Virtualization exam. View the exam blueprint at https://mylearn.vmware.com/mgrReg/plan.cfm?plan=64180&ui=www_cert.
- How vSphere High Availability works
- The basics of clusters
- Understanding failure types and failure response
- Monitoring HA virtual machines and appliances
- Using heartbeats
- Creating and configuring clusters
- Configuring admission control
- Best practices: Networking, interoperability, and cluster monitoring