News

New VMware Fling Diagnoses DRS

It allows admins to peek under the Distributed Resource Scheduler's hood.

• By Keith Ward
• 06/27/2016

Flings are, at least according to official VMware policy, experimental programs. They are unsupported tools typically meant to make a virtualization admin's life easier. Although recognized by VMware, they won't necessarily become official, shipping products. Sometimes they do, sometimes they don't.

It's likely, however, that the just-released fling DRS Doctor will become an official product in the future, since it does something very useful: it allows admins to diagnose issues with DRS -- vSphere's Distributed Resource Scheduler -- without having to call for help.

Senior Technical Marketing Architect Matthew Meyer, in a blog post today, explained that DRS is essentially a "black box." DRS moves virtual machines (VMs) around on different hosts, attempting to maximize the VMs' efficiency by, for instance, moving an overloaded VM to a host with more memory or CPU availability. While it works well, it's nearly impossible to know why a VM is moved.

Hence DRS Doctor, Meyer blogged:

"DRS Doctor records information about the state of the cluster, the advanced settings applied, the workload distribution, the virtual machine entitlements, performance demand, the recommended DRS moves, and more. Even better, DRS Doctor writes all this data into a log file that requires no special tools to read."

Meyer showed an example of how DRS Doctor works. He took a DRS cluster that was in balance -- i.e., the number of VMs didn't overburden the cluster -- and fired up many more VMs, unbalancing the cluster. As DRS started to migrate VMs to other hosts, DRS Doctor kept a running log of why the VMs were moved. Meyer was enthusiastic: "Here you can get a dump of every VM on every host in the cluster. It will show the current entitlement, demand, ready time, active memory, entitled memory, and any swapping. It's glorious!"

Flings can sometimes become shipping products very quickly. One of VMware's most important new products, for example, is the vSphere Client, used to manage vSphere from a desktop, laptop or other device. The new version, based on HTML instead of the outdated and insecure Flash client (known as the C# client), came out as a fling in late March 2016. In May, VMware stated that the new client will replace the C# client in the next version of vSphere.