[one-users] Sync State / Sanlock

[Ricardo Duarte]

Hi there,

Something I find missing in OpenNebula is a "sync state" functionality.
OpenNebula could monitor hosts and update the relationships between instances and hosts dynamically.
So, for example, when a host fails we could manually fix the problem by "virsh create" the deployments on a new server, and OpenNebula would pick the new host for the instances.
Currently, the machines stay as "UNKNOWN".

Also related is the potential danger "UNKNOWN" states present when the system datastore runs on shared storage.
So, on my last example:
- I would start the instances on a new host. 
- Users on Sunstone would still see the machines as "UNKNOWN" and can restart the machines
- Both instances would start writing on the same file, leading to corruption

To prevent that OpenNebula ccan/should make use of  sanlock. OpenNebula would be required to act as the lock manager.
By syncing state we could limit conflicts, and by using sanlock we could make it fail proof.

Regards,
Ricardo
 		 	   		  
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