Creating a disk array
A disk array is created using a set of Active Array Candidate
pdisks.
Migrating an existing disk array to a new RAID level
The SAS RAID controller supports migrating an existing
RAID 0 or 10 disk array to RAID 10 or 0, respectively. This allows
you to dynamically change the level of protection of a disk array
while preserving its existing data.
Deleting a disk array
To preserve the data on the disk array, you must first
back up all files in the logical volumes and file systems on the disk
array before removing the disk array from its volume group.
Adding disks to an existing disk array
Some controllers support adding disks to existing RAID
level 5 or 6 disk arrays, which allows you to dynamically increase
the capacity of a disk array while preserving its existing data.
Using hot spare disks
Hot spare disks are used to automatically replace a disk
that has failed in a redundant RAID environment.
System software allocations for SAS controllers
AIX has system software
resources allocated for the maximum number of attached devices, the
maximum number of command elements, and the total size of all outstanding
data transfers by active commands. The following procedures describe
how to view and change those settings.
Drive queue depth
For performance reasons, you might want to change the disk
command queue depth. The disk queue depth limits the maximum number
of commands that AIX software
can issue concurrently to that disk at any time. Increasing a disk queue depth might improve disk performance by increasing
disk throughput (or I/O) but might also increase latency (response
delay). Decreasing a disk queue depth might improve
disk response time but decrease overall throughput. The queue depth
is viewed and changed on each individual disk. When changing the disk
queue depth, the command elements and data transfer window on the
parent adapter might also need to be changed.
Multiple I/O channels
The PCI Express 3.0
(PCIe3) SAS adapter family supports multiple I/O channels. This support
enables the adapter device driver to process multiple interrupts in
different threads simultaneously, thereby potentially improving performance.
Increasing the number of channels that are used by an adapter might
improve disk performance by increasing disk throughput (or I/O), but
might also increase kernel-thread processing speed. The ideal number
of I/O channels must not be more than the number of RAID arrays that
are optimized on an adapter or lesser than the number of physical
processors that are assigned to the system partition. The number of
I/O channels can be viewed and changed on each individual RAID adapter.
AIX command-line interface
Many tasks used to manage the SAS RAID controller can be
performed by using the AIX command
line instead of using the SAS Disk Array Manager.
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