Belkin XM Commander Bedienungsanleitung PDF herunterladen (Seite 25)

# xm restore ttylinux.xen

This will restore the state of the domain and restart it. The domain will carry on

as before and the console may be reconnected using the xm console command, as

above.

4.3 Live Migration

Live migration is used to transfer a domain between physical hosts whilst that domain

continues to perform its usual activities — from the user’s perspective, the migration

should be imperceptible.

To perform a live migration, both hosts must be running Xen / xend and the destina-

tion host must have sufﬁcient resources (e.g. memory capacity) to accommodate the

domain after the move. Furthermore we currently require both source and destination

machines to be on the same L2 subnet.

Currently, there is no support for providing automatic remote access to ﬁlesystems

stored on local disk when a domain is migrated. Administrators should choose an

appropriate storage solution (i.e. SAN, NAS, etc.) to ensure that domain ﬁlesystems

are also available on their destination node. GNBD is a good method for exporting a

volume from one machine to another. iSCSI can do a similar job, but is more complex

to set up.

When a domain migrates, it’s MAC and IP address move with it, thus it is only possible

to migrate VMs within the same layer-2 network and IP subnet. If the destination node

is on a different subnet, the administrator would need to manually conﬁgure a suitable

etherip or IP tunnel in the domain 0 of the remote node.

A domain may be migrated using the xm migrate command. To live migrate a do-

main to another machine, we would use the command:

# xm migrate --live mydomain destination.ournetwork.com

Without the --live ﬂag, xend simply stops the domain and copies the memory image

over to the new node and restarts it. Since domains can have large allocations this

can be quite time consuming, even on a Gigabit network. With the --live ﬂag xend

attempts to keep the domain running while the migration is in progress, resulting in

typical ‘downtimes’ of just 60–300ms.

For now it will be necessary to reconnect to the domain’s console on the new machine

using the xm console command. If a migrated domain has any open network con-

nections then they will be preserved, so SSH connections do not have this limitation.

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Belkin XM Commander Bedienungsanleitung Seite 25