HSG80 ACS Solution Software V8.6 for Windows NT and Windows 2000 Installation and Configuration Guide

Planning Storage 2–17
Figure 2–12. Mirrorsets maintain two copies of the same data
Figure 2–13. Mirrorset example 2
Keep these points in mind when planning mirrorsets:
■ Data availability with a mirrorset is excellent but comes with a higher cost—you need
twice as many disk drives to satisfy a given capacity requirement. If availability is your
top priority, consider using dual-redundant controllers and redundant power supplies.
■ You can configure up to 20 mirrorsets per controller or pair of dual-redundant
controllers. Each mirrorset may contain up to 6 members.
■ Both write-back cache modules must be the same size.
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CXO7288A
A'A
B'
B
C'C
Mirror drives contain
copy of data
Operating
system
view
Actual
device
mappings
Mirrorset
CXO4594B
Disk 1
Block 0
Block 1
Block 2
etc.
Disk 2
Block 0
Block 1
Block 2
etc.
Virtual disk
Block 0
Block 1
Block 2
etc.