[one-users] How-to set RAM on Running KVM VM in CentOS 6.2x86 + openNebula v3.6

Ruben S. Montero rsmontero at opennebula.org
Wed Aug 22 03:54:22 PDT 2012 

Hi,

Just to answer the initial question from Junix, OpenNebula 3.6 does not
support hot-resize of CPU and MEMORY. As described in this thread, this can
be achieved somehow by interacting directly with the hypervisor although it
may lead to an inconsistent VM state in terms of resouce consumption.

 Given the interest show in this thread we will evaluate its implementation
for future versions.

Cheers and thanks for your great feedback!

Ruben

On Wed, Aug 22, 2012 at 11:06 AM, André Monteiro <andre.monteir at gmail.com>wrote:

> Hello,
>
> There is a more pratical and fast way:
> - open virt-manager and click for VM details
> - shutdown VM on OpenNebula
> - change RAM and CPU on virt-manager, it will update libvirt xml correctly
> - restart machine on OpenNebula
>
> The only catch is that OpenNebula doesn't know about this change and can
> overcommit resources.
>
> --
> André Monteiro
>
>
>
>
> On Wed, Aug 22, 2012 at 8:17 AM, cloud.b.lab <cloud.b.lab at zoho.com> wrote:
>
>> **
>> Junix,
>>
>> *There is an indirect method*, *but I do not recommend that as it will
>> send wrong and incorrect signals to OpenNebula Monitoring program and if
>> you do not have fast hands, your VM will end up in "unkn" state.*
>>
>> Again I am saying I it is not a  recommend practice and you don't try  it
>> in a non test environment.
>>
>>
>> If you would like to try it for information purpose , do the following:
>>
>> 1. Create a test vm and login.
>>    e.g.   153 oneadmin oneadmin centos63  runn   10   *1024M* onehost
>>    0d 00h12
>>
>> 2. Verify the total memory using "free" command
>>
>> 3. Go to the machine running libvirt [means your OpenNebula Node]
>>
>> 4. Get the doamin ID using                     virsh list
>>
>> 5. Get a xmldump of running domain         virsh dumpxml <Domain-ID>
>>  <file-name>
>>     e.g.  virsh dumpxml 7 > /var/lib/one/template/one-149
>>
>> 6. Open the XML and change the memory values, Save. Assume currently it
>> is 1048576.
>>   <memory>2095104</memory>
>>   <currentMemory>2095104</currentMemory>
>>
>> 7. Destroy the running domain                 virsh destroy 6
>>
>> 8. List all doamins in Shut-off state          virsh list --all
>>
>> 9. If it is there in shut-off state, undefine it          virsh undefine
>> <DOAMIn-NAME>
>>       e.g. virsh undefine one-149
>>
>> 10. Recreate the doamin using the XML
>>       e.g. virsh create /var/lib/one/template/one-149
>>
>> 11. Connect through VNC , login as root and check with "free". You will
>> see a higher MEM value
>>
>> 11. Give onevm top ,Wait for some time: OpenNebula reports the following.
>>
>> 153 oneadmin oneadmin  centos63   runn    5      *2G* onehost      0d
>> 00h24
>>
>>
>>  Thanks and regards,
>> Anil Kumar
>>
>>
>>
>> ---- On Tue, 21 Aug 2012 22:38:39 -0700 *cloud.b.lab<cloud.b.lab at zoho.com
>> >* wrote ----
>>
>> As per my limited understanding:
>>
>> The  RAM size you specify in the VM template using "MEMORY=xxxx"
>> translates to "Maximum available memory" for an active domain.
>>  Hence, while the domain being active , I think one cannot go beyond the
>> available/max mem.
>>
>> If you edit the XML file through libvirt and force change the Maximum
>> memory value to anything higher, you may end up in Kernel Panic situation.
>>
>> If you would like to try it , do the following:
>> 1. Create a test vm
>> 2. Verify the total memory using "free" command
>> 3. Go to the machine running libvirt
>> 4. Get the doamin ID using                               virsh list
>> 5. Save the current state of doamin using          virsh save <Doamin_ID>
>>  <Filename-with-domain-name>
>>     (so that you have a copy of it)
>> 6. Restore the doamin      using                        virsh
>>  <Filename-with-domain-name>
>> 5. Edit the doamin XML using                            virsh edit
>> <DOMAIN_ID>
>> 6. Try to change values for <memory> and <currentMemory> tags to a higher
>> value divisible by 1024.
>>      Assume current <memory> is 1048576.
>> e.g.
>>  <memory>2095104</memory>
>>   <currentMemory>2095104</currentMemory>
>> 7. Try to reboot the doamin                              virsh reboot
>> <DOAMIn-ID>
>> 8. Check available memory using "free"
>> 9. Try issue setmaxmem command to increase memory to 2095104   virsh
>> setmaxmem <DOAMIn-ID> 2095104
>>
>> oneadmin at onehost:~$ virsh setmaxmem 4 2095104
>> error: Unable to change MaxMemorySize
>> error: Requested operation is not valid: cannot resize the maximum memory
>> on an active domain
>> 10. Try to increase available memory
>> oneadmin at onehost:~$ virsh setmem 4 2095104
>> error: Requested memory size 2095104 kb is larger than maximum of 1048576
>> kb
>>
>> Hope this helps.....
>>
>> Regards,
>> Anil.
>>
>>
>>
>> ---- On Tue, 21 Aug 2012 10:42:41 -0700 *Lawrence Chiong<
>> junix88 at gmail.com>* wrote ----
>>
>> Hello,
>>
>> Can anyone guide me a step-by-step guide on HOWTO change/update RAM on a
>> fly / running VM (KVM). Because I tried changing my VM template (in
>> sunstone)  its Memory (e.g. from 2048M to 4096M) and then reboot my KVM VM
>> but changes made doesn't take effect. So I tried manually changed the
>> .../deployment.0 file and update the Memory element and update also the
>> vm_pool table on body field +Memory element to 4096M then I restarted
>> "oned" + "sunstone" so with mysqld BUT still the memory being updated
>> doesn't changed.
>>
>> Any help is very much appreciated.
>>
>> Thank you.
>>
>> Junix
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>
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-- 
Ruben S. Montero, PhD
Project co-Lead and Chief Architect
OpenNebula - The Open Source Solution for Data Center Virtualization
www.OpenNebula.org | rsmontero at opennebula.org | @OpenNebula
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