??? Youcan use the
operating system volume management to group these ???disks??? into arrays. With RAID-1
disks, this configuration delivers the benefits of using a dedicated I/O subsystem with
its own cache and processing power while leveraging striping for simplicity. With
RAID-S arrays youget the benefit of the dedicated I/O subsystem and further simplify
disk management by a striping multiplier effect. An array of five ???disks??? at the operating
system level could map back to five arrays of four disks each in the I/O
subsystem. This configuration maps a logical disk seen by Oracle to 20 physical disks
in the underlying I/O subsystem. Figure 7-3 illustrates a logical drive on the database
server mapping to horizontal sections across multiple RAID-S arrays.
Flexibility, Manageability, and Disk Arrays
Many systems today use some type of RAID technology that groups multiple individual
disk drives, also referred to as spindles, into arrays. Each disk array is then treated
Figure 7-2. Dedicated I/O subsystems
Oracle Instance
Operating System
I/O Memory Cache
Volume 1
RAID-5 Array
Volume 2
RAID-5 Array
Volume 3
RAID-1 Array
Volume Manager
Database Server
Dedicated I/O Subsystem
Oracle and Disk I/O Resources | 167
as a single logical disk for the purpose of planning I/O.
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