cl.cam.ac.uk/research/srg/netos/papers/2005-migrationnsdi-
pre. The migration from palantir to boromir can be broken down into a series
of steps or interactions between the two Xen servers:
1. Pre-Migration: The Feisty domain is running on palantir and is an
active domain.
2. Reservation: A request for migration is issued to the on palantir, which then
checks and confirms that resources are available on boromir. Xend then
reserves a VM container of the required size on boromir. If xend is unable to
get the resources it needs on boromir, then nothing will be done further, and
the domain will continue to run as is without any changes on palantir and
the relocation effort will be abandoned.
3. Iterative Pre-Copy: Memory pages are transferred from palantir to boromir
starting with all the pages and only then with the pages that were changed
during the initial transfer. Eventually all of the pages will be copied to
boromir.
4. Stop-and-Copy: The running domain on palantir is suspended and all its
network traffic is redirected to boromir. At the end of this stage, there is a
suspended copy of the domain on boromir in addition to the one suspended
on palantir. The suspended domain on palantir is still the primary copy and
in case of any failure at this stage, it will be resumed on palantir.
5. Commitment: At this stage if there are no errors or failures, boromir will
send an indication to palantir that it has a consistent image of
the domain.
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