[libvirt] Execute script on migration

Radek Hladík radek at eadresa.cz
Mon Oct 12 10:37:22 UTC 2009


Short question: What is the best way to run some script on VM migration?

Detailed description:
We use own system for volume management. Its based on md and we found it very
flexible. Basic idea is that we have md mirror everywhere we can. This suits
great for libvirt: We have a disk on iSCSI server, its "partioned" using
device mapper, the resulting "partition" is member of md raid1, that raid is
exported via iSCSI to the libvirt node, it is on the node included in another
md raid1 and that "final" md raid is used as storage by the VM. This provides
high level of abstraction that allows us to migrate  the storage to another
disk, another iSCSI server, etc...
The only glitch is on live migration of the VM. It is possible to assemble and
run the array on two nodes. Also all superblock modifications are done on
first write to the array. However it would be more secure to stop the array
after the source vm stops and before destination vm starts.
What is the best way to run some script in this particular moment? I know we
could create a new storage driver but I am not sure that it is the best option.

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