Eric Blake <ebl...@redhat.com> writes: > On 05/16/2017 11:00 AM, Markus Armbruster wrote: > >>>>> # periodic mode. (Since 2.8) >>>>> # >>>>> +# @block-incremental: enable block incremental migration (Since 2.10) >>>>> +# >>>> >>>> What's "block incremental migration" and why should I care? >>> >>> This is good, I will try. >>> >>> "block incremental migration assumes that we have a base image in both >>> sides, and then we continue writting in one of the sides. This way we >>> need to only migrate the changes since the previous state where it was >>> the same in both sides". >>> >>> I am not sure what to put there, really. >> >> Well, to suggest something, I'd first have to figure out WTF incremental >> block migration does. Your text helps me some, but not enough. What >> exactly is being migrated, and what exactly is assumed to be shared >> between source and destination? >> >> Block migration is scandalously underdocumented. > > If I have: > > base <- active > > on the source, then: > > block migration without incremental creates: > > active > > on the destination (the entire disk contents are migrated). Conversely, > block migration WITH incremental assumes that I have pre-created 'base' > on the destination (easy to do, since base is read-only so it can be > copied prior to starting the migration), and the migration results in: > > base <- active > > on the destination, where only the contents of active were transferred > by qemu.
Can you draft a documentation comment for @block-incremental?
