Re: [libvirt] [PATCH V6] support offline migration

On 09/11/2012 08:35 AM, Daniel P. Berrange wrote: >> >> Do we really need a new user-visible flag, or can we make this work >> automatically without having to involve the user? >> On the other hand, what happens if we do keep this as a user-visible >> flag? Should 'virsh migrate --offline' silently ignore the flag if the >> guest is online, or should it error out stating that the guest is >> running and not offline? >> >> Also, I think we NEED to error out if the guest is offline but the >> --persistent flag is not set; that is, an offline migration only makes >> sense if the persistent flag has been requested, but I think that 'virsh >> migrate --persistent' should automatically be smart enough to do an >> offline migration. > > No we must not do that. If a guest has shutoff we cannot assume that > the user / app wants to copy it across to the other host. eg consider > this scenario > > admin a: check if guestfoo is running > admin b: check if guestfoo is running > admin a: migrate guestfoo barhost > admin b: migrate guestfoo wizzhost > > IMHO step 4 should fail unless the admin explicitly requested > that they want to copy across the offline config Good point - the new flag is necessary, and must be user-visible. At which point, do we argue that use of the MIGRATE_OFFLINE flag automatically implies MIGRATE_PERSISTENT, or should it be an error unless the user explicitly requests both flags?