Users Guide
Related Information:
See the following:
l "Organizing Data Storage for Availability and Performance"
l "Comparing RAID Level and Concatenation Performance"
l "Controller-supported RAID Levels"
l "Number of Physical Disks per Virtual Disk"
l "Maximum Number of Virtual Disks per Controller"
Considerations for RAID 10 and 50 on PERC 3/SC, 3/DC, 3/QC, 4/SC, 4/DC, 4e/DC, 4/Di,
4e/Si, 4e/Di, and CERC ATA100/4ch Controllers
On the PERC 3/SC, 3/DC, 3/QC, 4/SC, 4/DC, 4e/DC, 4/Di, 4e/Si, 4e/Di, and CERC ATA100/4ch controllers, there are special considerations when implementing
RAID 10 or RAID 50 on a disk group that has disks of different sizes. When implementing RAID 10 or RAID 50, disk space is spanned to create the stripes and
mirrors. The span size can vary to accommodate the different disk sizes. There is, however, the possibility that a portion of the largest disk in the disk group
will be unusable, resulting in wasted disk space. For example, consider a disk group that has the following disks:
Disk A = 40 GB
Disk B = 40 GB
Disk C = 60 GB
Disk D = 80 GB
In this example, data will be spanned across all four disks until Disk A and Disk B and 40 GB on each of Disk C and D are completely full. Data will then be
spanned across Disks C and D until Disk C is full. This leaves 20 GB of disk space remaining on Disk D. Data cannot be written to this disk space, as there is no
corresponding disk space available in the disk group to create redundant data.
Comparing RAID Level and Concatenation Performance
The following table compares the performance characteristics associated with the more common RAID levels. This table provides general guidelines for
choosing a RAID level. Evaluate your specific environment requirements before choosing a RAID level.
Table 3-1.RAIDLevelandConcatenationPerformanceComparison
NOTE: The following table does not show all RAID levels supported by Storage Management. For information on all RAID levels supported by Storage
Management, see "Choosing RAID Levels and Concatenation."