Databases Reference
In-Depth Information
• Read I/O can be satisfied from the cache. The subsystem can employ some type of
algorithm to sense I/O patterns and preload the cache in anticipation of pending
read activity.
Note that you must back up the cache in the subsystem with some type of battery so a
power failure doesn't result in the loss of data that was written to the cache, but hasn't
yet been written to the physical disk. Otherwise, data that Oracle assumes made it to
disk may be lost, thereby potentially corrupting the database.
Figure 7-2
illustrates a
database server with a dedicated I/O subsystem.
Figure 7-2. Dedicated I/O subsystems
Oracle's engineered systems and storage
Oracle's highest performing engineered systems for the Oracle Database, the Oracle
Exadata Database Machine and the SuperCluster contain dedicated Exadata Storage
Server cells. Why did Oracle use this approach?
For many years, getting I/O configurations right for storage attached to Oracle Database
servers was problematic due to the number of vendors involved and the lack of focus
on the potential negative performance impact of mismatched storage to workloads and
