Common controller and disk array management tasks

You can perform various tasks to manage SAS RAID disk arrays.

Use the information in this section to manage your RAID disk arrays.

Using the Disk Array Manager
The Disk Array Manager is the interface for performing various tasks with disk arrays.
Preparing disks for use in SAS disk arrays
Use this information to prepare disks for use in an array.
Secure data deletion for Array Candidate pdisks that are formatted to RAID block size
Use this information to erase data from Array Candidate physical disks (pdisk) that are formatted to a block size that is compatible with SAS RAID.
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
Migrating an existing disk array to a new RAID level is not supported by the SAS RAID controllers in this system.
Viewing the disk array configuration
Use this procedure to view SAS disk array configurations on your server.
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.
Using hot-spare disks
Hot-spare disks are used to automatically replace a disk that has failed in a redundant RAID environment. For disk arrays, it is important to note that a hot spare disk will only replace a disk in an array of similar device class as that of the hot spare. Therefore, you need different hot spare disks to fully cover all the array device classes under the adapter. For example, a 4K SSD hot spare is needed for an array of 4K SSDs and a 4K HDD hot-spare disk is needed for an array of 4K HDDs.
Viewing IBM SAS disk array settings
This procedure enables you to view SAS disk array attributes and settings.
Viewing IBM SAS pdisk settings
This procedure enables you to view SAS pdisk attributes and settings.
Viewing pdisk vital product data
You can display a pdisk's vital product data (VPD).
Viewing controller SAS addresses
View SAS addresses (worldwide IDs) associated with each of the controllers ports.
Controller SAS address attributes
Interpret the results of viewing the controller SAS addresses.
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.
Considerations for solid-state drives (SSDs)
It is important to understand controller functions when using solid-state drives (SSDs).

Parent topic: SAS RAID controllers for AIX

Last updated: Wed, September 09, 2020