There have been a number of updates done to the backend of Maintenance Mode in vSphere 6.5 that will make VI admins very happy:
- Faster host evacuation times
- Priority evacuation for templates and Powered-on VMs.
Let me explain…
Faster host evacuation times
Evacuation times in the past have been acceptable, but as innovation continues to occur, we wanted to improve this aspect which will potentially shrink the need for current maintenance windows in your offices (faster evacuation = faster completion of updates/upgrades = smaller maintenance window requirements). What is really being done now is evacuation of Powered-off VMs in parallel. Before vSphere 6.5, these evacuations were done in a serial fashion. This would take quite a bit more time, whereas with vSphere 6.5, all of these evacuate in parallel, significantly dropping the evacuation time. As you will see with the table below, we have roughly an 85% percent change in evacuation times between 6.0 and 6.5.
vCenter has a maximum number of 100 VM re-register threads, which means if you have less than 100 VMs on a host that is being evacuated, these numbers will be the highest. With more than 100 VMs you will still see this ~700% performance increase but it may be slightly lower because of the 100 re-register thread process cap.
Priority evacuation for templates and Powered-on VMs.
In previous versions of vSphere, Powered-off VMs were not prioritized over Powered-on VMs, which generally isn’t a problem. However, if you wanted to power-on a powered-off VM, you might have to wait for a while for it to be moved (waiting behind a number of large powered-on VMs). This can be frustrating. What’s worse is that templates were never prioritized either which meant that if a VI admin wanted to use a template (deploy or clone) while a host evacuation was occurring, you would be unable to do that usually until the very end of a host evacuation because it was never prioritized. So anytime a template itself, content library items, or vRA blueprint templates tried to deploy while their templates were located on a host that was being evacuated, it would bring the workflow to a halt.
With vSphere 6.5, templates are prioritized above Powered-On VMs to allow for the continuity our customers require, bringing this challenge down to only a few seconds, rather than potentially taking minutes and minutes.
For more information, see the vSphere 6.5 DRS Performance White Paper HERE.