Hi Mayank,
As you have mentioned that with 7 host cluster you have 1 host failure tolerance, so when you select the option “Allow Virtual Machines to be powered on even if they violate availability constraints” it will allow you to poweron more VM's. so lets see what will happen as a result:
1. If you kepp on deploying VM's by enabling the above option. the cluster or VMware HA will not reserve resources for failure, it will start utilizing the resources which were reserved earlier for Failover.
So incase of failover it will poweron the VM's which have high priority, but only thing is that it should have resources available only then it will be able to poweron the VM's (even High Priority ones).
for Example: you have 5 Host with 10GB of RAM, and 1host failure capability. So if average utilization is 8GB on each host, it will reserve around 8GB of memeory out of cluster resources for failover, and you will not be able to poweron the VM's even if there is RAM available, but when you select the option “Allow Virtual Machines to be powered on even if they violate availability constraints” It will let you use reserved 8GB as well.
So now if you keep on deploying VM's till you use remaining 8GB, that means each host is reaching its 10GB and all of a sudden a host crash, i.e around 10GB of resouces are required to poweron the VM's but now as each server reached it's limit of 10GB, you will not be able to poweron the VM's as there are no resources.
So it's your responsibility, if you are confident that your environment is robust go ahead and select the option and enjoy, but if Bad luck comes then you are gone.
only option would be to poweroff Low priority VM's on hosts which didn't crash and get the hight priority Vm's powered on them.
Best of luck
Regards
