Introduction to Virtualization - Oracle Solaris 10 System Virtualization Essentials - page 22

Figure 1.11 Migrating a VE: Warm Migration
Figure 1.12 shows live migration, which differs from warm migration in terms
of the length of service outage. This outage is short enough that users do not
notice it. Further, applications running on other systems are not affected by the
outage. Unlike warm migration, which briefly pauses the VE while its memory
pages are copied to the destination, live migration methods copy the VE while it is
running. After the memory pages have been copied, the VE is paused and a final
set of data is transferred. Control of the VE then passes to the target system. This
transfer of control usually takes less than one second.
Both warm migration and live migration require the use of shared storage for
the OS, applications, data, and swap space.
Figure 1.12 Migrating a VE: Live Migration
Another form of mobility is the conversion from a physical environment to a
virtual environment, and from one virtualization technology to another. When dis-
cussing these activities, we use the letters “P” and “V” as a shorthand notation for
“physical” and “virtual,” respectively. For instance, moving an existing OS instance
from a physical computer to a virtual machine provided by a hypervisor is called
P2V . All four permutations are possible, and are shown at a high level in Table 1.1.