Hi,
As others told you already, this is the expected behavior. The reason
is very simple. All the VMs expect their allocated memory to be
available and might try to use it. And when that happens and the
memory is not there, the VMs will crash. That is not something you
typically want.
You can configure Memory over-commitment to allow this behavior.
Typically for desktop VMs that are not all using all the memory at the
same time. See for example the docs here
https://www.ovirt.org/documentation/administration_guide/#memory_optimiza...
and here
https://www.ovirt.org/documentation/administration_guide/#Cluster_Optimiz...
for explanation.
I also recommend enabling at least one of Enable Memory Balloon
Optimization and/or KSM control to allow nodes to rebalance free
memory. You should also set the Guaranteed memory for VMs as explained
in the above links to limit ballooning aggressivity.
Best regards
--
Martin Sivak
ex-oVirt maintainer of this area
On Mon, Sep 7, 2020 at 9:38 PM KISHOR K <smileyface.524(a)gmail.com> wrote:
Hi All,
I'm new to Ovirt and not having a perfect experience with Ovirt yet.
I ran into a strange issue today when I tried to create a new VM with 32GB in ovirt. VM
creation basically due to an error, pasted below.
Cannot run VM. There is no host that satisfies current scheduling constraints. See below
for details:, The host host-01 did not satisfy internal filter Memory., The host host-01
did not satisfy internal filter Memory.
After some troubleshooting, I found that there was enough available memory (around 120 GB
free ) in the host to host new VM and there were around 10 VMs already running on this
host.
But, I noticed that ovirt is actually scheduling and creating VM based on "Max free
Memory for scheduling new VMs" value, which seems to be set/updated based on total
allocated memory for all VMs running on the host and it's not really the then consumed
memory by running VMs.
Can anyone help to explain if it is some kind of bug in ovirt or it expected behavior?
If it is expected behavior, is there any possibility to change it to make sure VM is
created based on actual free memory?
Thanks a lot in advance for your support.
/Kishore
/Kishore
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