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Oracle Tips by Burleson

Disk I/O Tuning

Chapter 4: Disk Shadowing or Mirroring 

Figure 4-2: Example of Disk Mirroring

So far we have discussed basic RAID technology (RAID - Redundant Arrays of Inexpensive Disks.) RAID can be either software based or hardware based. Software based RAID never performs as well as hardware based RAID, in some cases software RAID actually performs worse than individual disks. RAID controllers are readily available so there is no need to depend on software RAID.

RAID—Redundant Arrays of Inexpensive Disks 

The main strengths of RAID technology are its dependability and IO bandwidth. For example, in a RAID5 array, the data is stored as are checksums and other information about the contents of each disk in the array. If one disk is lost, the others can use this stored information to re-create the lost data. However, this rebuild of data on-the-fly causes a massive hit on performance. In RAID 1, RAID 10 and RAID 01 failed disks are immediately replaced by their mirror with no performance hit. This makes RAID very attractive. RAID 5 has the same

The above text is an excerpt from:

Oracle Disk I/O Tuning
Disk IO Performance & Optimization for Oracle Databases
ISBN 0-9745993-4-4 

by Mike Ault

Oracle Consulting Services

Burleson Oracle Consulting offers Senior Oracle consultants which are available for all areas of Oracle support.  Common Oracle consulting support activities include short-term Oracle tuning, Oracle database troubleshooting, Oracle9i and Oracle10g migration, Oracle9iAS App Server consulting, Oracle design reviews and Oracle requirements evaluation support. Oracle support and Oracle consulting services are priced by the hour, so you only pay for what you need. These one-time Oracle consulting services commonly include:

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