Re: About virsh(1) and Postcopy migration

> * Does the same waiting happen when using options (2) and (3) above? No. The explicit "virsh migrate-postcopy" request expects the user to decide when to switch to post-copy by monitoring the migration. > * While running migration tests switch to postcopy appears to >   happen within 2 seconds of starting migration. >   - Is that reasonable time to switch from pre-copy to postcopy? No, that's not very reasonable. Basically every memory page access would have to be delayed until the page is transferred from the source host. >   - Is there an ideal time to wait before switching to postcopy? Not really. As the name suggests this is meant as a timeout, i.e., switch to post-copy if pre-copy migration is taking too long and thus is unlikely to ever converge. So logically the timeout should be long enough to give pre-copy migration to do its job. In this case, switching to post-copy is an alternative approach to CPU throttling for helping migration to converge. > * The feature page below suggests to wait until one cycle of RAM migration has completed >   -> https://wiki.qemu.org/Features/PostCopyLiveMigration  Right, that's definitely a good approach as only memory pages that changed during migration will have to be transferred from the source.