Page History

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• Admin/User while registering the template provides an input whether tools are installed on the template(or can be done using update template API).
• If the user deploys a virtual machine with a template that does not have XS tools / VMware tools and later if he/she installs the tools on the VM then he can inform Cloudstack using using updatevirtualmachine API. After installation of tools and updating the virtual machine, user needs to stop and start the vm from cloudstack in order for dynamic scaling of CPU and RAM for that VM. The reason why we need to stop start the VM after updating is we need to set static max memory to some higher value before VM starts so that we can dynamically scale the VM upto static max.

Hypervisor Changes

Xenserver

 To facilitate scaling up RAM for the VMs in xenserver Dynamic Memory Control(DMC) to change the amount of host physical memory assigned to any running virtual machine without rebooting it.

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• new dynamic max (y) <= static max and  
• new dynamic min (y / memory_overprovisioning_of_cluster) >= static min.

Further reading - http://support.citrix.com/servlet/KbServlet/download/32307-102-691300/reference.pdfhttp://wiki.xen.org/wiki/XCP_FAQ_Dynamic_Memory_Control#Introductionreading 

Vmware -

DeployVmCmd - 
During the initial deployment of the VM we enable the flags hotAddCpu and hotAdd memory true. These flags will be turned on if the guest OS supports it. Read http://partnerweb.vmware.com/comp_guide2/pdf/VMware_GOS_Compatibility_Guide.pdf

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During scaling up of vm, the new requested RAM and CPU are set if the flags are turned on.

Limitation - 1 - After dynamically scaling memory user "might" need to run a couple of commands on Linux OS for new memory to take affect --> Further Reading

Limitation* - 2 - 2 *if If a VM is initially assigned a RAM of less than 3gb then it cannot be dynamically scaled beyond 3gb. Holds true for for Linux 64 bit and windows 7 32 bit guest os. Further Reading

Limitation - 3 - Hot add vcpu will fail If the number of cores per socket is not 1 and virtual machine hardware version=7. Further Reading 

DB Changes

• Introducing a global config - enable.dynamic.scale.vm. Enables/Diables dynamically scaling a vm. This can be used to turn off the feature and is available at the zone level. By default the feature is turned off for upgrade reasons.
• Introducing a global config - scale.retry. By default the value = 2. This is for number of tries before failing the scaling.
• A new column in "vm_template" table named "dynamically_scalable" of type tinyint(1) and the value is 1 if template contains XS/VMWare tools inorder to support dynamic scaling of VM cpu/memory otherwise 0
• "user_vm_details" table holds key value pair with key "enable.dynamic.scaling" and value is true if VM contains XS/VMWare tools inorder to support dynamic scaling of VM cpu/memory otherwise false

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