KVM fixed memory - ballooning?

hansm

Active Member
Feb 27, 2015
61
3
28
In PVE 4.4 when creating a new VM, at the tab Memory there's a new checkbox "Ballooning" when "Use fixed size memory" is selected. I thought ballooning is only used with dynamic memory assignment (https://pve.proxmox.com/wiki/Dynamic_Memory_Management#Ballooning). Also the "Help" button doesn't explain the option for fixed memory.

Why do we have this new checkbox? Maybe an update of help and wiki pages is needed?
 

dcsapak

Proxmox Staff Member
Staff member
Feb 1, 2016
5,638
581
133
32
Vienna
the ballooning checkbox indicates if the vm gets the virtual balloon device.
in fixed memory mode, qemu sets no target size of the memory, so it handles it automatically.

if you choose automatically allocate memory in range
we set the target memory value and qemu behaves like the description in the documentation

but yes, thanks this is missing in the docs
 

Mecanik

Member
Mar 2, 2017
116
2
23
29
in fixed memory mode, qemu sets no target size of the memory, so it handles it automatically.

Can you elaborate that ? Because it really doesn't make any sense, "fixed mode" but it's still dynamic...
 

mjw

New Member
Jan 5, 2016
21
3
3
45
So fixed memory size means the memory is never available for the host or other VMs, even if ballooning is on and the VM doesn't use the memory itself? What are the reasons for using fixed size memory (as the default)?
 

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