User's Manual

252 Virtual Disks
disk fails, the virtual disk continues to function. The data is read from
the surviving mirrored pair disk. This feature provides the best failure
protection, read and write performance. Your system must have at
least four disks to use RAID 10. For PERC controllers with firmware
version 6 and above, RAID 10 also allows to create a single span virtual
disk with 22 or 26 physical drives.
–
Intelligent Mirroring —Automatically calculates the span
composition based on the physical disks you select.
Spans are not displayed on this screen. Select
Continue to view the
span grouping on the
Summary screen (Create Virtual Disk Advanced
Wizard (Step 4 of 4).)
Storage Management calculates the optimum span composition in the
following manner:
• Determining span calculation:
- Calculating the number of disks that can be utilized from the
selected disks.
- Maximizing the number of spans in order to increase the I/O
performance
• Determining the mirror for the physical disks:
The mirror is determined in a way that ensures maximum possible
redundancy. The algorithm also tries to match a physical disk for its
mirror to a disk that is closest to it in size. However,
Intelligent
Mirroring
gives priority to size over redundancy.
The algorithm determines the candidate mirror in the following order:
• Across connectors at the same level of enclosure and of same size
• Across connectors in the enclosure that are not at the same level
but of same size
• Across enclosures connected to same connector and to a disk of
same size
• Within the enclosure with a physical disk of acceptable size
difference
• Across connectors at the same level of enclosure and of acceptable
size difference