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If I/O performance across
the array is unsatisfactory, the solution is to add more controllers and disks. The
entire set of disks becomes a black box that either works or doesn??™t work as a unit.
Figure 7-3. Combining host-based striping and an EMC I/O subsystem
Disk 5
Oracle Instance
Operating System
I/O Memory Cache
Volume Manager
RAID-5 Array RAID-5 Array RAID-5 Array RAID-5 Array RAID-5 Array
Logical Disk A
Disk 1 Disk 2 Disk 3 Disk 4
Database Server
Dedicated I/O Subsystem
Volume Manager
168 | Chapter 7: Oracle Performance
The most useful configuration is one that balances manageability with flexibility. For
example, consider a system with 1,000 disks. Neither a single array of 1,000 disks
nor a set of 1,000 individual disks is likely to be appropriate. Perhaps 50 arrays of 20
disks each would provide the needed I/O performance without any undue administrative
burden. If less flexibility is needed, 20 arrays of 50 disks are more suitable. On
the other hand, grouping all the disks into one array may be the simplest way to
manage a system with only five disks.


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