The xend daemon accepts migration requests from
the localhost by default. To allow the migration target to accept incoming
migration requests from a remote host, you must modify the destination
host's xen-relocation-hosts-allow parameter in the /etc/xend-config.
sxp file. There is no authentication provided, so for security reasons you
must restrict the hosts that are allowed to migrate.
If you are running a firewall, you may need to create explicit iptables rules to
permit incoming migration connections.
Typical migrations result in a downtime of as little as 60-300ms.
You will need to reconnect to the console of the domain on the new Xen
server after the migration. Your existing console connection will not be
carried over along with the migration.
Saving and Restoring a Domain
The current state of a running domain is saved in a file on the disk. Xend restores
the state of the domain by using this file. This is similar in concept to the hibernation
feature of a laptop. During hibernating, a laptop saves an image of the disk state and
shuts itself. To come out of the hibernation, it uses the saved disk image to restore
the running state.
In this section we will learn how to save an active domain to a file that can later be
used to restore the file to the active state either on the same server or on a different
Xen server. You must ensure that you have enough disk space to save the image files
before you try to save a domain to an image file.
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