User's Manual

242 Virtual Disks
This feature provides better data redundancy and read performance,
but slower write performance. Your system must have at least three
disks to use RAID 5.
– Select
RAID 6 for striping with additional distributed parity. This
selection groups n disks as one large virtual disk with a capacity of (n-
2) disks. The virtual disk remains functional with up to two disk
failures. RAID 6 provides better read performance, but slower write
performance. Your system must have at least four disks to use RAID 6.
– Select
RAID 10 for striping over mirror sets. This selection groups n
disks together as one large virtual disk with a total capacity of (n/2)
disks. Data is striped across the replicated mirrored pair disks. When a
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.