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Oracle Tips by Burleson |
Disk I/O Tuning
Chapter 4:
RAID Technology
Unless you’ve
been living in seclusion from the computer mainstream, you will have
heard of disk striping, shadowing, and RAID. Let’s take a brief look
at them and how they are used in Oracle.
Disk striping is
the process by which multiple smaller disks are made to look like
one large disk. This allows extremely large databases, or even
extremely large single-table tablespaces, to occupy one logical
device. This makes managing the resource easier since backups only
have to address one logical volume instead of several. This also
provides the advantage of spreading I/O across several disks. If you
will need several ten's or hundreds of gigabytes of disk storage for
your application, striping is the way to go. One disadvantage to
striping: If one of the disks in the set crashes, you lose them all
unless you have a high-reliability array with hot swap capability.
Striping is RAID 0.
Figure 4-1 shows
an example of 4 disks using 3 stripes per disk. This allows larger
logical disks that would be allowed from a single disk. It also
spreads the data across more platters allowing a higher IO rate. All
of the stripe 1 slices form one logical disk, as do all of the
stripe 3 slices and the stripe 3 slices, so we have created 3 larger
logical disks with 4 times the possible IO rate of any of the disks
individually.
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
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For more
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