Raid Ime; Figure 4. Example Of Distributed Parity Across Two Blocks In A Stripe (Raid 6) - Intel AFCSASRISER User Manual

The following figure shows a RAID 6 data layout. The second set of parity drives are denoted
by Q. The P drives follow the RAID 5 parity scheme.
Segment 11
Segment 16
Parity (P17-P20)
Parity is distributed across all drives in the array. When only three hard drives are available for
RAID 6, the situation has to be that P equals Q equals original data, which means that the original
data has three copies across the three hard drives.

RAID IME

An IME volume can be configured with up to ten mirrored disks (one or two global hot spares
can also be added).
Mirroring Enhanced (IME) volume with three mirrored disks. Each mirrored stripe is written
to a disk and mirrored to an adjacent disk. This type of configuration is also called RAID 1E.
®
Intel RAID Software User's Guide
Provides data redundancy, high read rates, and good performance in most
environments. Can survive the loss of two drives or the loss of a drive while
Strong Points
another drive is being rebuilt. Provides the highest level of protection against drive
failures of all of the RAID levels. Read performance is similar to that of RAID 5.
Not well suited to tasks requiring lot of writes. A RAID 6 virtual disk has to
generate two sets of parity data for each write operation, which results in a
significant decrease in performance during writes. Disk drive performance is
Weak Points
reduced during a drive rebuild. Environments with few processes do not perform
as well because the RAID overhead is not offset by the performance gains in
handling simultaneous processes. RAID 6 costs more because of the extra
capacity required by using two parity blocks per stripe.
Drives
3 to 32
Segment 1 Segment 2
Segment 6 Segment 7
Segment 12
Parity (P13-P16)
Parity (Q17-Q20)

Figure 4. Example of Distributed Parity across Two Blocks in a Stripe (RAID 6)

Figure 5
Segment 3 Segment 4
Segment 8 Parity (P5-P8)
Parity (P9-P12) Parity (Q9–Q1
Segment 13
Parity (Q13-Q16)
Segment 17 Segment 18
shows the logical view and physical view of an Integrated
Parity (P1-P4) Parity (Q1-Q4)
Parity (Q5-Q8) Segment 5
Segment 10
Segment 9
Segment 14 Segment 15
Segment 19 Segment 20
13