Intel AFCSASRISER User Guide - Page 24

RAID 6 - Distributed Parity and Disk Striping, RAID 5

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Uses Strong Points Weak Points Drives Table 3. RAID 5 Overview Provides high data throughput, especially for large files. Use RAID 5 for transaction processing applications because each drive can read and write independently. If a drive fails, the RAID controller uses the parity drive to recreate all missing information. Use also for office automation and online customer service that requires fault tolerance. Use for any application that has high read request rates but low write request rates. Provides data redundancy, high read rates, and good performance in most environments. Provides redundancy with lowest loss of capacity. Not well suited to tasks requiring lot of writes. Suffers more impact if no cache is used (clustering). If a drive is being rebuilt, disk drive performance is reduced. Environments with few processes do not perform as well because the RAID overhead is not offset by the performance gains in handling simultaneous processes. 3 to 32 RAID 5 RAID Adapter ABCDEF Available Capacity N=# disks C = Disk Capacity Available Capacity = (N*C)(N-1) /N A B P1 C P2 D P3 E F Data Striping & Striped Parity RAID 5 Figure 3. RAID 5 - Data Striping with Striped Parity RAID 6 - Distributed Parity and Disk Striping RAID 6 is similar to RAID 5 (disk striping and parity), but instead of one parity block per stripe, there are two. With two independent parity blocks, RAID 6 can survive the loss of two disks in a virtual disk without losing data. Table 4 provides an overview of RAID 6. Uses Table 4. RAID 6 Overview Provides a high level of data protection through the use of a second parity block in each stripe. Use RAID 6 for data that requires a high level of protection from loss. In the case of a failure of one drive or two drives in a virtual disk, the RAID controller uses the parity blocks to recreate the missing information. If two drives in a RAID 6 virtual disk fail, two drive rebuilds are required, one for each drive. These rebuilds do not occur at the same time. The controller rebuilds one failed drive at a time. Use for office automation and online customer service that requires fault tolerance. Use for any application that has high read request rates but low write request rates. 12 Intel® RAID Software User's Guide

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12
Intel
®
RAID Software User’s Guide
Table 3. RAID 5 Overview
Figure 3. RAID 5 - Data Striping with Striped Parity
RAID 6 - Distributed Parity and Disk Striping
RAID 6 is similar to RAID 5 (disk striping and parity), but instead of one parity block per
stripe, there are two. With two independent parity blocks, RAID 6 can survive the loss of two
disks in a virtual disk without losing data.
Table 4
provides an overview of RAID 6.
Table 4. RAID 6 Overview
Uses
Provides high data throughput, especially for large files. Use RAID 5 for
transaction processing applications because each drive can read and write
independently. If a drive fails, the RAID controller uses the parity drive to
recreate all missing information. Use also for office automation and online
customer service that requires fault tolerance. Use for any application that
has high read request rates but low write request rates.
Strong Points
Provides data redundancy, high read rates, and good performance in most
environments. Provides redundancy with lowest loss of capacity.
Weak Points
Not well suited to tasks requiring lot of writes. Suffers more impact if no
cache is used (clustering). If a drive is being rebuilt, disk drive performance
is reduced. Environments with few processes do not perform as well
because the RAID overhead is not offset by the performance gains in
handling simultaneous processes.
Drives
3 to 32
RAID Adapter
ABCDEF
A
C
P3
B
P2
E
Data Striping &
Striped Parity
RAID 5
Available Capacity
N=# disks
C = Disk Capacity
Available Capacity =
(N*C)(N-1) /N
P1
D
F
RAID 5
Uses
Provides a high level of data protection through the use of a second parity block in
each stripe. Use RAID 6 for data that requires a high level of protection from loss.
In the case of a failure of one drive or two drives in a virtual disk, the RAID
controller uses the parity blocks to recreate the missing information. If two drives
in a RAID 6 virtual disk fail, two drive rebuilds are required, one for each drive.
These rebuilds do not occur at the same time. The controller rebuilds one failed
drive at a time.
Use for office automation and online customer service that requires fault
tolerance. Use for any application that has high read request rates but low write
request rates.