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Re: [Xen-users] Xen ballooning problem.

On Tuesday, December 19, 2017 5:22:39 PM CET Jason Long wrote:
>  Thank you for your reply but I mean is "KVM is also the better option for
> memory ballooning according to most users who accuse XEN of not returning
> unused RAM that has been previously shared with other VMs. KVM, unlike XEN
> is close to dedicated servers and users claim that KVM is way faster. Many
> users also admire the fact that KVM is more frequently updated which in
> turn leads to firmer security." Please see
> "https://cloudcone.com/blog/kvm-vs-xen-knowing-the-differences-and-picking-> 
> the-best/".

I think the " not returning " part comes from people who don't fully 
understand how Xen works.

With Xen, even the "host" is a guest. (Dom0)
In most default installations, the dom0 starts with all the memory. When you 
start a new VM, the required memory is removed from the dom0 and given to the 
When the VM is stopped, the memory is not automagically handed back to the 
dom0. You need to do this yourself (or add it to your management toolkit).

I set up my Dom0's to a fixed amount of memory and disable the ballooning part 
as this makes more sense in this context.

KVM works ontop of the host, which means that when memory is released by a VM, 
it does go back to the host.

KVM is not closer to the hardware than Xen is. But with KVM, the host is 
closer than the dom0. Which does mean that any benchmarking on the host itself 
is likely showing a slight performance benefit.
When looking at the VMs, however, I would doubt KVM to be better performing.

The main reason why I am preferring Xen over KVM is the ability to create true 
snapshots (eg. including RAM) and being able to create a seperate storage 
domain. I have not seen a similar option in KVM.


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