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The Greening of IT
94 How Companies Can Make a Difference for the Environment

offers virtual disks as ordinary SCSI devices. On the SAN side, SVC inte-
grates various storage subsystems, even multivendor, and takes care of the
correct block mapping between the SAN devices and the virtual disks for the
computers. Figure 6.3 illustrates how it works.

Virtual View
Physical View

Disk A Disk B
Disk C

ptg

Disk C
Disk B
Disk A
These materials have been reproduced by Pearson IBM Press, an imprint of Pearson
Education, Inc., with the permission of International Business Machines Corporation
®
from IBM Redbooks publication REDP-4413-00 The Green Data Center: Steps for the
Journey (http://www.redbooks.ibm.com/abstracts/redp4413.html?Open). COPYRIGHT
© 2008 International Business Machines Corporation. ALL RIGHTS RESERVED.
Figure 6.3 Storage virtualization: virtual view and physical view

The following points make the SVC an attractive tool for an energy-
efficient storage strategy:

■ Data migration from older to newer, more efficient systems can happen
transparently.
■ Tiered storage enables you to use media with a smaller energy footprint
while the SVC cache improves its performance.
■ Consolidation of the system’s individual storage devices to virtual storage
has the same effect—increasing storage utilization—as is shown for
server virtualization.