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SteveR2345
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vSphere 6.7 HA

Hi, forward from previous discussion. Looking for some advice on this setup if possible please...

I've been wondering if I only keep the reservation on the critical VM and remove it from the others, would it be possible to use resource shares to support failover for the critical machine. i.e.:

Host 1 has one VM-A 6TB fully reserved all host memory. Shares set to High

Host 2 has one VM-B 6TB no reservation but all host memory allocated. Shares set to Low

Host 3 has one VM-C 6TB no reservation but all host memory allocated. Shares set to Low

If Host 1 fails, will the shares allow VM-A to start on another host? Or would I be right in thinking it depends on the memory demand on the VM at the time? 

Thanks for any help on this.

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depping
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If you have 6TB reserved, then you need 6TB unreserved to be able to failover, nothing you can do to change this via shares etc. you need 6tb unreserved, and you will need a bit more as the VM itself also requires a small amount of reserved memory.

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depping
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If you have 6TB reserved, then you need 6TB unreserved to be able to failover, nothing you can do to change this via shares etc. you need 6tb unreserved, and you will need a bit more as the VM itself also requires a small amount of reserved memory.

SteveR2345
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Thanks Duncan, looks like one more expensive host required so!

Steve

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depping
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is there a requirement for a full reservation? You could also lower the reservation just with 1TB? But make sure to check "unreserved" capacity first, as even VMs without a reservation set on memory will reserve some resources

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SteveR2345
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According to SAP HANA the production workload must have a full reservation. I thought we might be able to remove them from the other workloads in the cluster to achieve it, but as you said that wont help unless we have a full 6TB available somewhere.

After speaking to our local VMware solution engineer, I believe it's possible to trigger python script from the vCenter alert for HA which in turn could stop the "non-critical" VM's. This could also be done via the vCSA event broker fling I'm told. Unfortunately we don't have the skills to develop and support this action but it's promising if a future release may make it accessible.

Thanks

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depping
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Yes, it would be an interesting solution indeed, and I actually have filed a feature request in the past to solve this exact problem.

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depping
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Just thinking about this, with VEBA this should not be rocket science. you could tag all the VMs which should be powered off when a failure occurs. and VEBA could simply trigger that script to power off the VMs when the event has occurred.  Without any experience with scripting of course this would be more challenging, but I am sure you could find a local consultancy company to help with this. Script for powering off VMs with a certain tag is relatively easy: https://www.running-system.com/vmware-power-cli-shutdown-power-off-all-vms-with-a-dedicated-vmware-t...