Preparing for Exadata - Oracle Exadata Recipes: A Problem-Solution Approach - page 145

How It Works
Sizing your DATA and RECO storage configuration and requirements is primarily a planning exercise. Each Exadata
Database Machine of the same configuration is going to have the same number of physical disk drives in the storage
cells. You will have 36 disks to work with on a Quarter Rack, 84 on a Half Rack, and 168 on a Full Rack. These can
either be 600 GB High Performance or 3 TB High Capacity disks, and your disk type selection will dictate your overall
raw storage capacity.
Configuring disk groups with ASM normal redundancy will leave you with half of your raw capacity for usable
database storage, and high redundancy will cut your usable capacity to a third of your raw capacity. Assuming that
you only store recovery structures in your RECO disk groups, the capacity available for database file storage will be
further reduced.
Table 6-1 provides a summary of Exadata usable disk capacity with both ASM normal and high redundancy
as well as with a 60:40 split between RECO and DATA , as is the default when you elect to perform backups internal
to Exadata.

Table 6-1. Exadata usable storage capacity

X2-2 Quarter Rack X2-2 Half Rack X2-2/X2-8 Full Rack

Storage Server Usable Capacity,
High Performance Disks, Normal
Redundancy

10.3 TB Usable
4.12 TB for Data

25.2 TB
10.08 TB for Data

50.4 TB
20.16 TB for Data

Storage Server Usable Capacity,
High Performance Disks, High
Redundancy

7.2 TB
2.88 TB for Data

16.8 TB
6.72 TB for Data

33.6 TB
13.44 TB for Data

Storage Server Usable Capacity,
High Capacity Disks, Normal
Redundancy

54 TB
21.6 TB for Data

126 TB
50.4 TB for Data

252 TB
100.8 TB for Data

Storage Server Usable Capacity,
High Capacity Disks, High
Redundancy

36 TB
14.4 TB for Data

84 TB
33.6 TB for Data

168 TB
67.2 TB for Data

6-6. Planning for ASM Disk Group Redundancy
Problem
You've decided your Oracle ASM disk group redundancy configuration using methods presented in Recipe 5-4 and
you wish to calculate your overall usable capacity for both DATA and RECO data files.

Solution
The shell script in Listing 6-1 can be used to show your overall usable capacity per database storage type. It will
prompt for your Exadata model configuration, desired ASM disk group redundancy, and the percentage to allocate for
RECO disk storage.