Raid 6 Configuration Guidelines; Comparing Raid 5 And Raid 6; Raid 5 And Raid 6 Comparison - EMC Symmetrix DMX-3 Product Manual

Data Integrity, Availability, and Protection
One member rebuild
Two member rebuild
RAID 6 configuration
guidelines
Comparing RAID 5
and RAID 6
Table 30
Uses two mirrors to represent the device: data mirror and parity
mirror.
Uses mirror invalid to indicate both logical and physical invalids. Uses mirror invalid to indicate logical invalid; uses the Physical
Supports both permanent sparing and dynamic sparing.
Uses special disk commands to perform XOR operations.
210 EMC Symmetrix DMX-3 Product Guide
In a one member rebuild, the data members rebuild like RAID 5, the
horizontal parity rebuilds like RAID 5, and diagonal parity rebuilds
using data from all data members.
In a two data member rebuild, the rebuild is segment by segment
recursively using both horizontal and diagonal parities. In a one data
member and horizontal parity rebuild, the data member is rebuilt using
diagonal parity. The horizontal parity is rebuilt using all data
members.
In a one data member and diagonal parity rebuild, the data member is
rebuilt using horizontal parity. The diagonal parity is rebuilt using all
data members.
In a horizontal parity and diagonal parity rebuild, both horizontal and
diagonal parity is rebuilt using all data member data.
The following are some guidelines to consider when configuring
RAID 6 devices:
BCVs can be RAID 6 devices.
SymmOptimizer Swap supports RAID 6 devices.
SRDF devices can be RAID 6 devices.
eSNAP source and destination devices can be RAID 6 devices.
A log device can be a RAID 6 device.
Concurrent Copy is supported with RAID 6.
Table 30 on page 210
RAID 6.

RAID 5 and RAID 6 comparison

RAID 5
describes the comparisons between RAID 5 and
RAID 6
Uses a single mirror to represent the overall state of the device.
Consistency table to indicate physical inconsistent.
Supports permanent sparing. If permanent sparing is not
successful on the first failure, no additional action is taken. If
permanent sparing is also unsuccessful after a second failure
(double-degraded mode), then RAID 6 dynamic sparing will be
attempted.
Uses Symmetrix hardware functionality to perform XOR
calculations.