Patrol Read; Disk Striping; Example Of Disk Striping (Raid 0) - Lenovo ThinkServer RD240 Software User's Manual

2.4.8

Patrol Read

2.4.9

Disk Striping

Patrol read involves the review of your system for possible drive errors
that could lead to drive failure and then action to correct errors. The goal
is to protect data integrity by detecting drive failure before the failure can
damage data. The corrective actions depend on the drive group
configuration and the type of errors.
Patrol read starts only when the controller is idle for a defined period of
time and no other background tasks are active, though it can continue to
run during heavy I/O processes.
You can use the MegaRAID Command Tool or the MegaRAID Storage
Manager to select the patrol read options, which you can use to set
automatic or manual operation, or disable patrol read. See
"Controller Property-Related Options,"
Read".
Disk striping allows you to write data across multiple drives instead of
just one drive. Disk striping involves partitioning each drive storage space
into stripes that can vary in size from 8 KB to 1024 KB. These stripes
are interleaved in a repeated sequential manner. The combined storage
space is composed of stripes from each drive. It is recommended that
you keep stripe sizes the same across RAID drive groups.
For example, in a four-disk system using only disk striping (used in RAID
level 0), segment 1 is written to disk 1, segment 2 is written to disk 2,
and so on. Disk striping enhances performance because multiple drives
are accessed simultaneously, but disk striping does not provide data
redundancy.
Figure 2.1

Example of Disk Striping (RAID 0)

Segment 1
Segment 5
Segment 9
Components and Features
or
Segment 2 Segment 3
Segment 6 Segment 7
Segment 10 Segment 11
Section 5.4,
Section 9.5, "Running a Patrol
Segment 4
Segment 8
Segment 12
2-7