CPU and RAM allocate permanently

[AdrianEM]

Hi,

I just wondering is there any possibility that we can allocate CPU, RAM, disk space for one of your Virtual machine permanently? It means that none of the rest machines would can take this ram, cpu for sharing even the vm is powered off? 

[MustafaSadek]

As far as i know .. the reservation make this task .. to reserve memory and cpu for vm .. this will guarantee resources be allocated for the vm even if it is powered off

[AdrianEM]

You know how to set it up?

[MustafaSadek]

Well if you click on vm setting then click on cpu or memory   , it will list more details about them and you will find  check box (reservation ) where you can type the mount of resources you want to reserve

[depping]

Keep in mind:

•  reservations only apply when VMs are powered on
• if you for instance reserve memory resources and power on the VM, then NO other VM can claim those resources, which means that if you run out of resources other VMs may experience a performance impact

Reservations are not often used to be honest. Why would you want to use them?

[Tibmeister]

Totally agree with @depping, the whole notion of reservations is counter productive, especially when you are talking about CPU reservations.  Vendors may claim that they "must have resource reservations", but that's from a position of being uninformed and a lot of CYA on their part so you can't over-provision your cluster and potentially cause their product to act slowly.

Reservations cause problems and are not a great resource management strategy.  If a VM is not using all 16 vCPU's it's assigned, let some other process use those dang CPU cycles.  Of course, monster VM's are a whole different beast unto themselves.

[MustafaSadek]

Thanks @depping for mentioning this point . This mean if vm reserved 5 GB memory for  example while it is powered on  and then we  shutdown it... the next power on for this vm will  need at least 5 GB memory  to make vm power on and if it didn't find at least 5GB  memory resource available then it won't power on as it has to guarantee 5 gb reserved . 

[depping]

It requires 5GB of unreserved memory, that is the keyword: unreserved. When it reserves it, it means that NO OTHER virtual machine can touch the memory. 

[MustafaSadek]

Thank you for declaration