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compute instance

asked 2019-01-29 05:24:47 -0500

lelunicu gravatar image

hi, i like to clarify how a VM (instance) is launched on compute.

when a instance is launched then in the memory is created vcpu,vnic so on coresponding to this VM.Then nova will boot the image using ceph?

tnx

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answered 2019-08-09 02:19:59 -0500

jayeshc gravatar image

I tried to write instance creation workflow, check if you find your answer there. https://jayeshc1990.wordpress.com/201...

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answered 2019-01-29 06:01:33 -0500

updated 2019-01-29 06:04:13 -0500

What happens depends on the hypervisor. The most commonly used hypervisor is KVM/qemu. In this case, Nova creates an instance description in XML and runs virsh commands to create the instance and to launch it. virsh translates the XML file into a qemu command line and runs it.

Before launching the instance, Nova works with Neutron to set up the network connections. There are many options. Usually, the instance's NIC is represented by a tap interface, which is plugged into a Linuxbridge or an Openvswitch bridge.

If the instance is launched from a volume, Nova also works with Cinder to set up the storage connections.

Ceph can be used to contain the instance's root disk, but it's not the only option. The default is putting the instance's root disk in a file on the compute node's file system. It can also be implemented as an LVM volume, and there are other options as well.

The Nova Architecture pagemay contain relevant information; I have not read it though. You may want to read the documentation under https://docs.openstack.org/nova.

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Asked: 2019-01-29 05:24:47 -0500

Seen: 37 times

Last updated: Aug 09