Information Technology Reference
In-Depth Information
The
ldm migrate
command can be issued with the option
-n
to request a dry
run that tests whether the migration is possible but does not actually migrate the
domain.
In
cold
migration, the domain must be stopped. It must also be in the
bound
or
inactive
state on the source machine. Cold migration consists of verifying ac-
cess to the domain's I/O resources. In particular, the virtual disks must be acces-
sible to both the source and the target. This step also ensures there are sufficient
resources to bind the domain after migration, and then transmits the domain's
description to the target machine. Once the domain is migrated, the domain on
the source machine is unbound (if it is currently bound to resources) and removed
from the source domain configuration. Cold migration applies only to domains
that are not running, but can be very helpful for planned migration of workloads
that can tolerate an outage with a shutdown and reboot. It is very fast, as only
descriptive information is transmitted between servers.
In
warm
migration, a running domain is suspended on the source machine and
resumed on the target machine without a reboot. Domain execution is suspended
while it is being migrated. This process may take a number of seconds or a few
minutes, depending on domain memory size and network speed, and on whether
the control domain has access to a cryptographic accelerator.
First, the domain managers on both source and target machines verify that
sufficient capacity to bind the domain on the target is available. Then, the target
system creates and binds a single-CPU version of the guest domain, and the source
machine removes all but one CPU from the running domain. Next, the source ma-
chine suspends the domain and removes its last CPU. The domain's memory con-
tents and state are then compressed, encrypted (using the cryptographic accelera-
tor if one is associated with the control domain), and transmitted from the source
to the target.
Processing is multithreaded and takes advantage of the CPU threads in the
control domain; it also exploits the cryptographic accelerator to ensure better per-
formance. Domain memory contents are always encrypted before transmission,
as it would be a significant security exposure to transmit a domain's memory
contents (which might include passwords or private information) as cleartext. The
domain is then restored on the target system and its remaining CPUs added. The
Oracle Solaris instance continues execution on the target machine with the same
disk storage, IP addresses, and MAC addresses as before, and applications resume
processing. Finally, the domain is unbound and removed from the source host's
domain configuration.
Warm migration is suitable for planned migration of any workload that can be
paused for a number of seconds.
A
live
migration capability is anticipated, in which a migrating domain will be
unresponsive for only a very small interval.
Search WWH ::
Custom Search