Wednesday, April 17 • 3:40pm - 4:20pm
Mothball a server

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This session will include the following subject(s):

Mothball a server:

Today when you stop a server, it remains on the hypervisor host.

Many users, with less cloud like workloads, want the ability to stop servers when they don't need them, but to retain IP addresses and current disk state (including ephemeral), so they can start it up at some time in the future.

From an operator perspective, this should take up minimal resources. Preferably, only storage space.

Lets look at how best to implement this within Havana. See Etherpad for discussions:

(Session proposed by John Garbutt)

Make Nova Stop/ Start operations release physical :

The current Nova stop/start schematics leave an instance associated to the same host, so the scheduler has to keep the resources on that host allocated so that the instance can be re-started. From a service provided perspective this means that it’s hard to offer any financial advantage to stopped instances since they are in effect still consuming the same amount of logical resources.

It’s already noted in the code that the current stop/start should really be renamed power-off/power-on since that is what they actually do.

We would like to be able to exploit boot from volume so that users can “stop” an instance preserving all of its network settings, metadata, instance_id, etc but remove the consumption of any physical resources. On start the instance would be re-scheduled to a new host.

The basic operations would be:
Stop: Power down the instance, and remove any local storage associated with the instance

Start: Reschedule the instance to a new host, and start the instance on that host as if it had been newly created (from a local disk perspective)

Restart: A combined Stop/Start command

Stop should always complete, even if the host the instance is currently running on is down.

Any data in volumes (including boot volumes)would be preserved. Any data in ephemeral discs would be lost.

It would seem logical to take this opportunity to rename the current stop/start to power-off/power-on and re-use the stop/start verbs for this operation.

(Session proposed by Phil Day)

Wednesday April 17, 2013 3:40pm - 4:20pm

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