8:14 p.m.
Medlyn, Dayne (VSL - Ft Collins) wrote:
Hi,
Hi Dayne, welcome to the list.
We have been looking into what some of the Libvirt-CIM wholes might be for our needs and
possibly how we can help close some of those wholes. I recently sat in on Dan Smiths
presentation on the Libvirt-CIM and need a little bit of clarification.
>From Dan's presentation it sounds like the ability to create a VM configuration
(currently we are most interested in Xen) already exists. Can someone help me understand
what that looks like right now? I presume it involves something like establishing a
configuration, adding components to it (such as memory, CPUs,
storage, network, etc.), posting that configuration to host (the xenstore for Xen?), then
starting the VM guest.
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.
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
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).
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.
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
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 =)
--
Kaitlin Rupert
IBM Linux Technology Center
kaitlin(a)linux.vnet.ibm.com