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6: A Most-Significant Step—“Virtualizing” Your IT Systems 95

Storage virtualization requires more effort than server virtualization, often
requiring us to rethink the existing storage landscape. During consolidation,
large amounts of data must be moved from the old systems to the consoli-
dated storage system. This can become a long task that requires detailed
planning. However, when done, the effect can be enormous because now stor-
age can be assigned to systems in the most flexible way.

Virtual Tapes

Tapes are the cheapest medium on which to store data. They offer the
largest storage volume at the lowest cost, which is the reason that they are the
optimal backup medium. Tapes have a long latency compared to disks. This is
not always a benefit. Currently, data centers are faced with a time limitation
for backing up and probably restoring their data because the time frames for
backups shrink, while the amount of data to back up expands. For this reason,
many sites prefer large disk-based backup systems instead of tapes.
Tape virtualization might be a solution to this problem. A virtual tape
server behaves just like a tape library, but a very fast one. This is made possi-
ble with internal disk arrays and a migration strategy to export to and import ptg
from real tape libraries.

Client Virtualization

A great potential in energy savings is client, or desktop, virtualization.
Various studies have estimated energy savings of more than 60 percent by
using client virtualization. In a typical workplace, installed PCs show very
low average usage rates. Except when launching an application, an office PC
spends most of its time waiting for the user to press a key or click a mouse.
However, the PC continues to need a considerable amount of energy to oper-
ate, heats up its surrounding environment, and produces noise. Desktop vir-
tualization can dramatically improve the situation.
The underlying principal of client virtualization is to replace the office
workstation with a box having a much smaller energy footprint. The needed
computing power is moved into the data center. Today’s virtualization tech-
niques make this approach even more attractive. The concept of client virtu-
alization—often called thin-client computing—is not a new concept and
goes back at least 15 years. In fact, thin-client computing where the server
does all the processing is similar in concept to the terminals we used to con-
nect to the mainframe before the advent of the PC.