OpenStack Compute (nova)

resize(migration) VS os-liveMigration

Asked by Ying Chun Guo

Can somebody explain to me the differences between the admin-action methods : migrate and os-liveMigration?

I noticed:
1. the method "migrate" invokes "resize" indeed with the parameter "flavor" setting as "None".
2. the method "migrate" takes no parameter, but "os-liveMigration" accepts the host name as a parameter.

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John Garbutt (johngarbutt) said : 		#1

live-migration keeps the VM "running" when moving machines

Migration moves the VM, but involves taking a snapshot of the terminated VM, then starting it on a new host (well, sort of).

Resize is designed to shutdown a VM and resize its disk to match the newly request flavour, this may involve moving to a new host that has enough room for the larger VM

It turns out migration is a resize without changing the size of the VM, but just does the moving host bit.

I hope that helps? If this is not clear in the documentation, are you OK to raise a documentation bug?

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Ying Chun Guo (daisy-ycguo) said : 		#2

There is a bug in the documentation - bug 1022653 - to describe this issue. And I'm designed to fix it. So I'm like to make sure my understanding is right.
Thanks, John.