IBM SAS RAID controllers, Manual

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Disk arrays use RAID technology to offer data redundancy and to provide improved data transfer rates
over single large disks. If a disk failure occurs, the disk can typically be replaced without interrupting
normal system operation.
Data redundancy
The disk array controller tracks how the data is distributed across the disks. RAID 5 and RAID 6 disk
arrays provide data redundancy, ensuring that data is not lost if a disk in the array fails. If a disk failure
occurs, the disk can typically be replaced without interrupting normal system operations. System
mirroring provides data redundancy by mirroring the same data across pairs of disks.
Supported RAID levels
The RAID level of a disk array determines how data is stored on the disk array and the level of
protection that is provided.
If a part of the RAID system fails, different RAID levels help to recover lost data in different ways. If a
single drive fails within an array, the array controller can reconstruct the data for the failed disk by using
the data stored on other hard drives within the array. This data reconstruction has little or no impact to
current system programs and users. The controller supports RAID levels 5 and 6 as well as system
mirroring. Not all controllers support all RAID levels. Each RAID level supported by the controller has its
own attributes and uses a different method of writing data. The following information provides details
for each supported RAID level.
Related concepts :
“PCI-X SAS RAID card comparison” on page 2
Use the table in this topic to compare the features of the various PCI-X SAS RAID cards for IBM i. There
are also images of adapters for you to view.
“PCIe SAS RAID card comparison” on page 5
Use the tables in this topic to compare the features of the various PCI Express (PCIe) SAS RAID cards for
IBM i. There are also images of adapters for you to view.
“PCIe2 SAS RAID card comparison” on page 10
Use this table to compare the features of the various PCI Express 2.0 (PCIe2) SAS RAID cards for IBM i.
“PCIe3 SAS RAID card comparison” on page 13
This table compares the main features of PCI Express 3.0 (PCIe3) SAS RAID cards.
Related information :
Device parity protection concepts
RAID 5:
Learn how data is written to a RAID 5 array.
RAID 5 stripes data across all disks in the array. RAID level 5 also writes array parity data. The parity
data is spread across all the disks. For a RAID 5 array of three disks, array data and parity information is
written in the following pattern:
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SAS RAID controllers for IBM i