I was trying to enable FT on a VM but secondary VM
wasn't powering ON. Post investigation I have identified quite interesting
stuff.
Max CPU usage for one host for FT is 8 (Even though the host cpu resources are high,by design for 6.0 max count is 8)
In our production setup, when checked the cluster and the cluster resources, they were maxed out, cause of which we were unable to power on the secondary FT VM.
In this setup, the host count in the cluster - 17.
Since HA and DRS are also configured on the cluster, we have reserve resources for failover and DRS purpose.
Recommendations:
Refer the below link for more information on FT in vsphere 6.0
Max CPU usage for one host for FT is 8 (Even though the host cpu resources are high,by design for 6.0 max count is 8)
Refer the below link for maximum guide for FT configuration.
https://www.vmware.com/pdf/vsphere6/r60/vsphere-60-configuration-maximums.pdf
Search for Fault Tolerance or FT in the document, you will be able find all the maximum details in this document.
https://www.vmware.com/pdf/vsphere6/r60/vsphere-60-configuration-maximums.pdf
Search for Fault Tolerance or FT in the document, you will be able find all the maximum details in this document.
In our production setup, when checked the cluster and the cluster resources, they were maxed out, cause of which we were unable to power on the secondary FT VM.
In this setup, the host count in the cluster - 17.
max vcpu count supported for FT is 8 per host, that results in 17*8 = 136
vcpu's can be used for FT feature in this cluster.
VM's on the cluster with FT configured - 18 (all 18 VMs were configured with 4 vcpu), which results in (18*4)*2(counting the secondary machine for FT) = 144 vcpu are currently in use on this cluster for FT.
VM's on the cluster with FT configured - 18 (all 18 VMs were configured with 4 vcpu), which results in (18*4)*2(counting the secondary machine for FT) = 144 vcpu are currently in use on this cluster for FT.
Since HA and DRS are also configured on the cluster, we have reserve resources for failover and DRS purpose.
Recommendations:
1) Either add one or two hosts to the cluster to power on the secondary FT vm
on this cluster.
2) Reduce the vcpu count for FT configured machines from 4vcpu to 2vcpu, if it is not required. (for non-critical VMs) which will help you accommodate move FT machines in the cluster.
Note:- Please do not forget to calculate the vCPU used for
FT VM and max of 8 vcpus can be used per host for FT.2) Reduce the vcpu count for FT configured machines from 4vcpu to 2vcpu, if it is not required. (for non-critical VMs) which will help you accommodate move FT machines in the cluster.
Refer the below link for more information on FT in vsphere 6.0
Link: http://www.vladan.fr/vsphere-6-features-long-distance-vmotion (Search for 6.0 Fault Tolerance)
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