On the VMware Community someone asked this question about restart priorities. At the same time I received a question on a similar topic via email. This particular question was as follows:
I have restart priorities defined on my cluster. However even if I place my virtual machines for which this order applies on one host and test a failure they seem to come online in the wrong order…
In vSphere HA you can define the restart priority for each individual virtual machine. Now this restart priority applies to the power-on task that is initiated by HA when a host has failed. Did you note that I emphasized power-0n attempt? Well there is a reason for that… it is the prioritization of the attempt itself. HA doesn’t wait for a virtual machine to power-on before it starts the next… it just does the power-on attempt and when it completes the next round will be attempted. This also means that if you use 3 different priorities it could happen that a “low priority” virtual machine is restarted literally seconds after a “high priority” virtual machine is. In the case of the person who asked the question he had a large database machine defined as “high priority” and an app as “low priority”. Unfortunately the database machine took minutes to power-on and report up, where the application took less than a minute.
Keep that in mind when defining the restart priorities for your virtual machine. Yes it will help, but only for prioritizing which virtual machine needs to be restarted first. This is not a guarantee your virtual machines will be completed booted up first,
Is there any advanced cluster setting that you can set to control the delay between the power on of high-medium-low priorities?
Also if you use a vApp to control the startup order of VMs and define delay times will a HA power-on obey these settings?
Duncan Epping says
No vSphere HA does not respect vApp Startup Orders. And I don’t know of an advanced setting to control a delay between the priority levels.
Heino Skov says
When I end up in this situation I usually play arround with the guest OS boot time options. So let the low priority machine has a higher timeout, to make it boot a little slower and make time for the DB server to come up.
But yeah, its some tricky, time-consuming tweaking to test.
Duncan Epping says
That is a nice work around Heino…
Something I’ve always wanted as an option is HA dependancy settings. I can’t imagine I’m the only one that would love to see HA know that these app servers are dependant on this SQL box over here. A simple “is VMware tools responding on SQL, great, away we go” would suffice.
Yes It’s a shame HA doesnt respect vApp startup orders/delays. It would be perfect for that