VMware's Distributed Resource Scheduler (DRS) is an important tool for solutions providers who are trying to optimize their customers' resources. DRS allocates resources based on application priority.
Aside from Distributed Resource Scheduler, performance and usage monitoring tools also play a major role in vSphere management. There are several factors to consider when deciding which tools will work best for you and your customers.
In this FAQ podcast, virtualization expert Eric Siebert explains how to properly configure Distributed Resource Scheduler and evaluate other vSphere management tools.
Read Eric Siebert's answers to other frequently asked questions on vSphere management.
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Distributed Resource Scheduler and vSphere management
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•How does Distributed Resource Scheduler work for balancing virtual machine (VM) workloads?
•How can I monitor resource usage on VMs and hosts?
•Is there a method for doing chargeback for resource usage in vSphere?
•What new resource controls are in the new version of vSphere?
•More resources on the Distributed Resource Scheduler
•About the expert
Distributed Resource Scheduler utilizes the vMotion feature to provide automated resource optimization through automatic migration of VMs across hosts in a cluster. DRS also provides automatic initial VM placement on any of the hosts in the cluster, and it also makes automatic resource relocation and optimization decisions as hosts or VMs are added or removed from the cluster. You can also configure DRS for manual control, so that it only provides recommendations that you can review and carry out.
DRS utilizes resource pools and clusters that combine multiple host resources into a single entity. Multiple resource pools can also be created so that you can divide the resources of a single or multiple hosts into separate entities. Currently, DRS will only migrate VMs based on availability and CPU and memory resource utilization. It does not take into account high disk or network utilization to load-balance VMs across hosts.
When a VM experiences an increased load, DRS first evaluates its priority against the established resource allocation rules. From there, if justified, it redistributes VMs among the physical servers to try and eliminate contention for resources. VMotion will then handle the live migration of the VM to a different host with complete transparency to end users. The dynamic resource allocation ensures that capacity is preferentially dedicated to the highest-priority applications while maximizing overall resource utilization.
When monitoring VM performance, you should rely on tools that are designed for virtual environments, because many operating system tools such as Windows Perfmon are not aware of the underlying virtualization layer and will often provide inaccurate results on certain counters and measurements. VMware's ESX and ESXi hypervisors and vCenter Server have built-in performance monitoring tools that you can use to more accurately monitor the performance of your hosts and VMs, and they are the best choice when monitoring VM performance.
VCenter Server provides configurable performance statistic collections so that you can view both real-time and historical statistics going back as far as you want. ESX and ESXi hosts that are not managed by a vCenter Server are limited to providing real-time statistics and only up to 60 minutes of historical statistics. Additionally, the esxtop and resxtop command-line utilities can provide great real-time information on a wide variety of relevant performance statistics and are very useful for performance troubleshooting. There are also a number of performance-related alarms that can be set so that you can be quickly alerted of performance problems in your environment. For more detailed reporting and monitoring, there are many third-party utilities available.
Currently, there is no method built into vSphere for this, and there are also very limited resource reporting capabilities. However, VMware does sell a separate product called vCenter Chargeback that fully integrates with vSphere and can perform cost analysis, measurement and reporting of resource usage. There are several third-party products such as VKernel Chargeback that can do this as well.
The new version of vSphere, which was released last week, will provide better control for storage I/O by allowing quality-of-service prioritization to be set on storage I/O activity. This control is enabled on a whole data store, and once a set level of latency is reached, then storage I/O is prioritized by shares or set levels of I/O operations per second. This new control will guarantee that critical VMs receive the priority they need to keep their performance intact.
About the expert
Eric Siebert is a 25-year IT veteran whose primary focus is VMware virtualization and Windows server administration. He is one of the 300 vExperts named by VMware for 2009. He is the author of the book VI3 Implementation and Administration and a frequent TechTarget contributor. In addition, he maintains vSphere-land.com, a VMware information site.