What’s new in vSphere 6.0- Changes in HA

By | 15/03/2015


Today I was reading one of the Duncan Epping’s blog and found one useful info related to HA so thought of sharing with you all.

We all are aware of DRS affinity and anti-affinity rules and we know the fact that HA doesn’t respect the VM-Host should rules and if any host fails then HA can restart the VM’s anywhere and not necessarily on the host to which VM’s has affinity rules tied up.

However on next invocation of DRS (default 5 minutes) this violation would be corrected by DRS itself and VM’s will return to the host according to the VM-Host affinity rules.

With vSphere 6.0 VMware has introduced one new advanced configurable option in HA. This setting is called “das.respectVmHostSoftAffinityRules”.

As the name itself suggests, this setting will let HA to respect VM-Host affinity rules when it can and can violate it when HA doesn’t have much choice. To make things clear let’s consider the below scenario.

We have 4 Esxi hosts and each host have 10 running VM’s. 3 VM (VM-a, VM-b, VM-c) on the host 2 has affinity rules configured to run only on host 2 and host 3. Now suppose host 2 fails and HA starts the failover. We have defined “das.respectVmHostSoftAffinityRules” in HA so HA ideally can restart VM-a, VM-b and VM-c on host 3 in accordance to the VM-Host affinity rules.

But suppose if the host 3 is already heavily loaded and running on nearly full capacity and it cannot accommodate any new incoming VM, then HA has no choice but to restart the VM’s elsewhere (may be on host 1 or host 4)

The second scenario can be none of the host where failed VM’s has affinity rules tied is available at the time of failover. In this case HA will behave just like it is doing till version 5.5 and can restart VM’s anywhere on the remaining nodes of the cluster.

Hit like and share this info if it is useful for you.

Category: VMware

About Alex Hunt

Hi All I am Manish Jha. I am currently working in OVH US as Operations Support Engineer (vCloud Air Operations). I have around 7 Years of IT experience and have exposure on VMware vSphere, vCloud Director,vSphere Replication, vRealize Automation, NSX and RHEL. If you find any post informational to you please press like and share it across social media and leave your comments if you want to discuss further on any post. Disclaimer: All the information on this website is published in good faith and for general information purpose only. I don’t make any warranties about the completeness, reliability and accuracy of this information. Any action you take upon the information you find on this blog is strictly at your own risk. The Views and opinions published on this blog are my own and not the opinions of my employer or any of the vendors of the product discussed.