[Libvirt-cim] What is the current state of VM guest creation/modification, storage pools, and metrics in Libvirt-CIM?

[Medlyn, Dayne (VSL - Ft Collins)]

Kaitlan 

> The define procedure is done using the DefineSystem() call of 
> the Virt_VirtualSystemManagementService provider.  The 
> DefineSystem() call takes the following parameters:
> 
> SystemSettings - an instance of the 
> Xen_VirtualSystemSettingData class ResourceSettings - an 
> array of Xen_ResourceAllocationSettingData (RASDs) instances 
> ReferenceConfiguration - a reference to an existing 
> Xen_VirtualSystemSettingData instance
> 
> The RASDs represent the various resources (disk, CPU, etc) 
> you would like your guest to have.
> 
> The provider then generates an XML that it passes to libvirt, 
> and libvirt handles defining the guest.  The libvirt-cim 
> providers don't talk to the Xen components directly; 
> everything is handled through libvirt.

This sounds as if it is just what we are looking for . Thanks for the detail.


> > Does this include configuring to boot from install media? 
> How about configuring for a network boot from which to do an install?
> 
> With fully virtualized Xen guests, you can specify the "BootDevice" 
> attribute of the Xen_VirtualSystemSettingData instance that 
> is passed in for the SystemSettings parameter.  The available 
> options are "fd", "hd", "cdrom" or "network".
> 
> For paravirtualized guests, the "Bootloader" and 
> "BootloaderArgs" are used to specify which bootloader to use 
> and what arguments to pass.
> 
> For more info:  http://libvirt.org/formatdomain.html#elementsOS

I am still a little fuzzy on network booting a paravirt guest, but I believe the details will come out as we get a bit further.

 
> > Does this interface also support modifying this 
> configuration, either live or off-line?  
> 
> Yes, you can add/remove/modify resources of a guest while it 
> is running or while it is offline  - as supported by the 
> underlying virtualization platform (Xen, KVM, etc).

Great!


> > Is there mechanism to validate new configurations before 
> committing them?
> 
> We don't do any validation as such.  The DefineSystem() call 
> tells libvirt to define a guest with the specified options.  
> If libvirt is unable to define the guest, we return an error 
> to the user accordingly.

This seems pretty reasonable.


> > Another aspect Dan talked about was Resource Pools.  I 
> realize there is work going on to enhance Resource Pools.  Is 
> the current implementation of Resource Pools limited to 
> storage pools?  What type of storage is supported (iSCSI, 
> NFS, Fibrechannel?, etc.)?
> 
> We currently represent the following pools:  disk, network, 
> processor, memory, graphics device, and input device pools. 
> Only disk and network represent actual virtual pools (as 
> defined by libvirt).
> 
> Libvirt supports the following storage types:  dir, 
> fs,netfs,disk,iscsi, logical.  All of these pools show up as 
> an instance of the DiskPool class.
> 
> libvirt-cim doesn't currently support 
> creation/deletion/modification of pools, so a user must 
> create a pool using libvirt tools.  Once the pool has been 
> created, libvirt-cim will generate and instance of the 
> DiskPool class to represent that pool.
> 
> More info on libvirt storage pools:  
> http://libvirt.org/formatstorage.html

Thanks again for the detail.


> > An area we are looking to help augment is around guest 
> metrics, at least those that can be collected from the host.  
> Of particular interest are counters.  Is there anyone 
> currently working on this that I should collaborate with?
> 
> No one is currently working on metrics.  There was some prior 
> work done 
> with Xen metrics for the sblim data-gatherer.   I'm not sure 
> the current 
> status of these plugins though.
> 
> We definitely haven't given it much thought as to whether it 
> would be better to work with the existing data-gatherer 
> framework, or if it would be better to develop a set of 
> metrics providers for the libvirt-cim project itself.  This 
> is definitely a good topic for additional discussion =)

This is what I had come to understand.  As we get a little farther we will make some proposals and see how the rest of the community feels about them.  Basically, I see a need for some sort of marriage between Libvirt-CIM and possible the sblim data-gatherer.  Libvirt-CIM may need to gather the guest data from the host, but feed it to the sblim data-gatherer for consumption.  This will take a bit more thought though.  Dan suggested something similar.


One more question.  Daniel Veillard mentioned someone may be working on VM cloning capability.  Do you know any details about it or who might be working on it?


Thanks again for all your help.


Dayne