Practical Cloud Knowledge: Install, Configure, and Manage - Deploying and Managing a Cloud Infrastructure - page 217

as if the nodes are connected locally even though they might be located in different geo-
graphic areas, as in different countries. For example, an organization has a global network
across its various offices using the Internet or WANs, but all the regional managers want
to be able to communicate with each other as if they were in a single office LAN. This is
possible with a VLAN. Another example is a large building network. All of the computers
are connected to the same large network, but it can be subdivided by floors or departments,
which is all done via software and settings of the computers and the routers and switches
in the network, without really altering the physical connections in the network. With a
VLAN, you can connect virtual machines and physical computers together.
VSAN A virtual storage area network is similar to a VLAN. It is meant to further sub-
divide a storage area network into smaller parts that can be made available to different
users. It is mostly meant for micromanaging the SAN.
Establishing Migration Requirements Migration can become a tricky endeavor, and some-
times a portion of data is lost in the process, as well as applications and systems no longer
working correctly or as expected, even losing performance. Some will attribute this degrada-
tion to the cloud environment, when really the problem is with a botched migration.
It is very important that the migration goes off perfectly, so requirements have to be
established by the business beforehand. Because your service provider will be the one to
usually handle all migration, we now have this saying that migration is no longer a tech-
nical issue but a business one. It is the business side of the organization that will make
use of the system and not the technical IT department, so the migration has to be in the
hands of a business user or manager with the support of a technical manager.
Storage Migration Storage migration is simply transferring the data contents of a reposi-
tory into a newer or more technologically advanced one, assuming that it is an upgrade and
not a downgrade.
Online vs. Offline Migrations Online migrations are done through the Internet by stream-
ing all of the data and the applications from the old system or repository right into the new
one. This usually happens automatically and is done via replication, so there is often perceived
disruption to the normal operations of the system. The only major requirement for this is that
the current networking infrastructure of the organization supports the large amount of band-
width that is needed to transfer large amounts of data. Most of the time the network provider
will require an extra charge for the bandwidth used.
On the other hand, offline migrations are done when online migration is not feasible to do in
a timely manner. The organization has to resort to saving all of the data, which needs to be
migrated, into multiple storage devices and then shipping them to the new service provider
so that the data can be uploaded into the system. Business managers and technical managers
or representatives have to be around to oversee the migration at the other end just to ensure
that everything is placed where it is supposed to be.
Physical to Virtual (P2V) Physical to virtual migration involves converting the soft-
ware side of a physical machine into files that can be migrated into a virtual machine.