[ovirt-users] Cannot create VM with custom memory amount

[TranceWorldLogic .]

Thanks Gianluca

On Wed, Jan 11, 2017 at 1:46 PM, Gianluca Cecchi <gianluca.cecchi at gmail.com>
wrote:

> On Wed, Jan 11, 2017 at 6:31 AM, TranceWorldLogic . <
> tranceworldlogic at gmail.com> wrote:
>
>> Thanks Ondra that link is useful,
>> Do you have any Idea why VDSM disable balloon concept for RHEV and use
>> for all non-RHEV ?
>>
>> Please refer to below link.
>> https://www.ovirt.org/documentation/sla/memory-balloon/
>>
>>
>> *"Currently the balloon memory device is being created by default by
>> libvirt for non RHEV environments, and VDSM disables it by default for
>> RHEV."*
>> Is there different technique use by RHEV ? Please provide me link for it
>> detail.
>> It will help me to compare ovirt and RHEV
>> *.*
>>
>> Thanks,
>> ~Rohit
>>
>>
> In effect it is strange.
> Inside official docs for RHEV 4.0 we have:
> Administration Guide
> https://access.redhat.com/documentation/en/red-hat-
> virtualization/4.0/paged/administration-guide/52-cluster-tasks
>
> "
> 5.2.2.2. Optimization Settings Explained
> Memory Balloon
> Selecting the Enable Memory Balloon
> Optimization check box enables memory
> overcommitment on virtual machines running
> on the hosts in this cluster. When this option
> is set, the Memory Overcommit Manager
> (MoM) will start ballooning where and when
> possible, with a limitation of the guaranteed
> memory size of every virtual machine.
> ...
> It is important to understand that in some
> scenarios ballooning may collide with KSM. In
> such cases MoM will try to adjust the balloon
> size to minimize collisions. Additionally, in
> some scenarios ballooning may cause sub-
> optimal performance for a virtual machine.
> Administrators are advised to use ballooning
> optimization with caution.
> "
>
> So it seems it is indeed possible to enable ballooning (note the
> considerations about KSM that could partially answer to your question...)
>
> But then in Virtual Machine Management Guide here
> https://access.redhat.com/documentation/en/red-hat-
> virtualization/4.0/paged/virtual-machine-management-
> guide/33-installing-guest-agents-and-drivers
>
> I see
> "
> 3.3.1. Red Hat Virtualization Guest Agents and Drivers
>
> virtio-balloon
>
> Virtio-balloon is used to
> control the amount of
> memory a guest actually
> accesses. It offers improved
> memory over-commitment.
> The balloon drivers are
> installed for future
> compatibility but not used by
> default in Red Hat
> Virtualization.
> "
>
> So it seems it is not possible to enable it for guests....
> Any clarification?
>
> Thanks,
> Gianluca
>
>
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