|  |
|
Oracle Tips by Burleson |
Disk I/O Tuning
Chapter 4: Disk Stripping
Figure 4-1: Example of Disk
Striping
Disk Shadowing or Mirroring
If
you have mission-critical applications that you absolutely cannot
allow to go down, consider disk shadowing or mirroring. As its name
implies, disk shadowing or mirroring is the process whereby each
disk has a shadow or mirror disk that data is written to
simultaneously. This redundant storage allows the shadow disk or set
of disks to pick up the load in case of a disk crash on the primary
disk or disks; thus the users never see a crashed disk. Once the
disk is brought back on-line, the shadow or mirror process brings it
back in sync by a process appropriately called “resilvering.” This
also allows for backup since the shadow or mirror set can be broken
(e.g., the shadow separated from the primary), a backup taken, and
then the set resynchronized. I have heard of two, three, and even
higher mirror sets. Generally, I see no reason for more than a
three-way mirror as this allows for the set of three to be broken
into a single and a double set for backup purposes. Shadowing or
Mirroring is RAID 1.
The
main disadvantage to disk shadowing is the cost: For a 200-GB disk
farm, you need to purchase 400 or more gigabytes of disk storage.
Figure 4-2 shows disk mirroring. In figure 4-2 disk group A is
considered the active group, disk group B is the "mirror" group.
Both disk group A and disk group B are maintained through
simultaneous writes.
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:
-
Answering
questions from your Oracle DBA technical staff
-
Repairing down
production Oracle database systems
-
One-time
Oracle tuning evaluation
-
Guru support
for your Oracle DBA
-
Installation
of Oracle application packages
For more
information, please visit
www.rampant-books.com
|
