Storage Area Networks For Dummies®

Chapter 10: Mirror, Mirror: Point-in-Time Copies
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Rotating PiT areas to provide Business Continuance Volumes
Time
6:00 a.m.
9:00 a.m.
12:00 p.m.
XYZ
application
XYZ
application
XYZ
application
Figure 10-3:
Rotating
your PiT
copy gives
you a quickrecovery
point more
than three
hours old.
PiT copy
XYZ
6:00 a.m.
PiT copy
XYZ
9:00 a.m.
Same PiT volume area
PiT copy
XYZ
12:00 p.m.
Most backup software packages are SAN-aware, so they can communicate
with the SAN hardware to make these copies automatically and do the rotation
for you. However, even if your software isn’t up to speed on SANs yet,
all backup software supports some type of scripting that can be used to do
the commands to create and mount the PiT copies to where they can be
backed up. You’re covered when it comes to integrating PiT into your current
backup schedules.
Creating a PiT copy offers an enormous advantage over standard tape
backup processes. When tape is too slow to restore from, an on-site PiT
of your critical apps saves you from a lot of headaches. And because disk
is much faster, easier to access, and more flexible than tape recovery, it
provides a great tool for IT departments to keep in their toolbox for critical
applications.
Save space
Running a SAN with PiT copies doesn’t force you to use a lot more disk space
than before. With a SAN, you don’t have to dedicate disk-copy areas on a oneto-one
relationship with your application data. Because you can move disks
around from server to server, you can move the PiT areas as well. You can
share the disks needed to make the PiT copies.