In this video, Russ Long introduces the DRS course by going through some of the basics of the DRS technology. Learn how DRS can help you clusters perform better and better utilize resources.
- [Narrator] The basics of any technology should be mastered prior to diving into the advanced details. So let's do a quick review of the basics of a DRS cluster. Now DRS is really a resource manager of a cluster. It allows the placement of virtual machines within the cluster to ensure that the cluster resources are drawn as equally as possible, among the host in a cluster. Now before we can just begin with the features of DRS, we should discuss the foundation, itself, the cluster.
Now the cluster is a group of hosts that we have combined administratively for the purposes of pooling resources together, to solve a problem administratively. Now, even though, we are combining, or amalgamating, these resources together, the amount of resources we can offer a virtual machine cannot exceed the size of the host in which it resides. Last, but definitely not least, our cluster should be provisioned with hosts that are built as similarly as possible.
This not only helps DRS but other cluster technologies as well. Remember, in a DRS configuration, depending on our automation level, VMs are fluid and will move through the cluster hosts, as necessary. The more similar the hosts are in the cluster, the less of a problem, we're going to have with vMotion. Please note, CPUs have to be within the same vendor family or live vMotions will fail.
So we will have processors from the same vendor within the same cluster and in an ideal world, we would want those processors to even be the same model. When we deploy a cluster in our ESX environment, DRS isn't the only option available to us. There are several technologies that we can put into play. High Availability, or HA, is a technology that responds to host failure within the cluster by restarting all the VMs located on that failed host to other active hosts in the cluster.
Resource pools allow us granular control of the allocation of resources to VMs. We can even prioritize certain Vms within the cluster to receive more resources. DRS is a load balancing technology and the focus of our course. vSANs, or virtual Storage Area Networks, amalgamate server hard disks into a single virtual SAN. EVC, or Enhanced vMotion Compatibility, allows processor features to be brought down to the lowest common denominator, making live vMotions or powered-on VM migrations compatible.
So what is the role of DRS within a cluster? Well, we already know that it is a resource management technology. It balances resource consumption across hosts in a cluster. It does this by moving or placing VMs within the cluster to less congested hosts. This can be done for both compute and storage resources, for initial placement of a VM or a powered-on migration of a VM to other less used hosts in the cluster. DRS, when paired with Distributed Power Management, can also be used to make the cluster more power-efficient.
Distributed Power Management is a major feature within a DRS cluster. DPM turns off any unneeded host within the cluster to save on power consumption. If, at a later time, the cluster needs that host, DPM will power back on the host and rebalance the VMs, using live migration. DRS and HA, as well, have the ability to apply rules that determine how VMs are placed within a cluster.
- An overview of DRS
- Migrating virtual machines and thresholds
- Configuring DRS
- Creating and editing clusters
- Working with Storage DRS cluster features
- Managing DRS cluster resources
- Enabling Distributed Power Management
- Troubleshooting DRS