I encounter this issue during the replacement of our old blade server. I just want to share the troubleshooting steps I did to justify the error.
We can't vMotion the VM server to the new blade server and we get this error The host host-3499 can not satisfy requested 2450 Mhz per vCPU for this VM. Maximum core frequency is 2444 Mhz per physical CPU.
- Obviously base on the error there is resources issue to justify please continue reading
- I just compare the CPU specs of the old balde server to the new blade server
Old Blade Server CPU Specs
New Blade Server CPU Specs
- Seems like the new blade server having more CPU to allocate but this is different when it's come to VM CPU reservation due to the CPU frequency ( old blade server has 2.50 GHz or 2500 MHz then the new blade server has 2.40 GHz or 2400 MHz )
To get the maximum MHz reservation that can set to VM with 6 CPU's
Here are the two formula we can use:
Formula 1: CPU Cores x The frequency MHz = Per Core MHz then Per Core MHz ÷ CPU Cores x No. of VM CPU = CPU reservation you can set to the VM
Formula 2: CPU Frequency x No. of VM CPU = CPU reservation you can set to the VM
Note: Convert the CPU frequency GHz to MGz
Example:
Old Blade Server:
Formula 1: 20 Cores x 2500 MHz = 50,000 MHz per core then 50,000 MHz per core ÷ 20 Cores x VM with 6 vCPU's = 15,000 MHz this is the CPU reservation you can set to the VM server with 6 vCPU's
Formula 2: 2500 MHz x 6 CPU's = 15,000 MHz this is the CPU reservation you can set to the VM server with 6 vCPU's
New Blade Server:
Formula 1: 28 Cores x 2400 MHz = 67,200 MHz per core then 67,200 MHz per core ÷ 28 Cores x VM with 6 CPU's = 14,400 MHz this is the CPU reservation you can set to the VM server with 6 CPU's
Formula 2: 2400 MHz x 6 CPU's = 14,400 MHz this is the CPU reservation you can set to the VM server with 6 CPU's
- As we can see to the computaion above, the new host CPU reservation can be setup is less than the old blade server, in this case it's not satisfied the VM reservation currently setup to the VM server. That's why we get issue during the vMotion and error related to resources issue.
- We can see below VM CPU reservation is 14700 MHz and Max is 15000 MHz our new balde server only can give Max reservation of 14,400 MHz.
- These values are more than the max frequency of the CPU.
- Adjust these values to match the destination host.
The CPU reservation of the VM in question is around:
- 14700 MHz with 6 vCPU = 14700/6 = 2450 per core These values are more than the max frequency of the CPU - To solved the issue adjust these values to match the destination host
For example, You can change the reservation as :
- 2400 *6 = 14400 MHz for the 6 vCPU VM This would allow the VM to migrate to the destination host.
Or you can disable the CPU reservation completely. This will also aloow the VMs to be migrated.
Note: VM have to be powered off before changing the reservation
- Now we justify the error. I hope you learn alot and I hope this can be use in your future journey exploring the VMware Products :) Thank you
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