RTM-ATCA-SXXX Overview
6806800H62B ATCA‐S201InstallationandUseGuide66
5.3.3 Software RAID levels and capabilities
RAID
Level
Description Data Layout Diagram
RAID4
Three or more disks are grouped in fashion where
all written data is available even when any single
disk drive is removed or fails. RAID4 employs
block level striping with a dedicated parity disk.
Disk 1
Disk 2
S0 S1
S2 S3
S4 S4
Stripe
Stripe
Stripe
RAID4
Disk 3
Parity
S0
S1
S2
S3
S4
Data
Parity
Parity
RAID5
Three or more disks are grouped in fashion where
all written data is available even when any single
disk drive is removed or fails. RAID5 employs block
level striping with a distributed parity disk.
This provides a significant advantage for RAID5 vs
RAID4 for write operations, because the bandwidth
of all disks is available for parity write operations.
Disk 1
Disk 2
S0 S1
S2
Parity
Parity S4
Stripe
Stripe
Stripe
RAID5
Disk 3
Parity
S3
S5
S0
S1
S2
S3
S4
Data
RAID6
Four or more disks are grouped in fashion where all
written data is available even when any two disk
drives are removed or fail. RAID6 employs block
level striping with two distributed parity disks.
While RAID6 provides a significant redundancy
advantage, each write spawns two additional parity
calculations, which in turn adds commensurate
loads on both the internal CPU and memory
systems.
Stripe
Disk 1
Disk 2
S0 S1
S2 Parity-P
Parity-P Parity-Q
Stripe
Stripe
Stripe
RAID6
Disk 3
Parity-P
Parity-Q
S4
S0
S1
S2
S3
S4
Data
Disk 4
Parity-Q
S3
S5
Parity-Q S6 S7 Parity-P
