HA access optimization
HA access characteristics can balance the controller workload.
With either of the HA RAID configurations, best adapter performance is achieved by defining HA access characteristics for each disk array such that the workload is balanced between the two controllers. Setting the HA access characteristics for a disk array specifies which controller is preferred to be optimized for the disk array and perform direct read and write operations to the physical devices.
View the HA access characteristics by completing the following steps.
- Navigate to the IBM® SAS Disk Array Manager by using the steps found in Using the Disk Array Manager
- Select Manage HA Access Characteristics of a SAS Disk Array.
- Select the IBM SAS RAID controller.
HA access characteristics are displayed on the IBM SAS Disk Array Manager screen, similar to the following screen.
+---------------------------------------------------------------------------------+
| IBM SAS Disk Array Manager |
| Move cursor to desired item and press Enter. |
| List SAS Disk Array Configuration |
| Create an Array Candidate pdisk and Format to RAID block size |
| Create a SAS Disk Array |
| Delete a SAS Disk Array |
| Add Disks to an Existing SAS Disk Array |
| Migrate an Existing SAS Disk Array to a New RAID Level |
| Configure a Defined SAS Disk Array |
| +--------------------------------------------------------------------------+ |
| | HA Access Characteristics of a SAS Disk Array | |
| | | |
| | Move cursor to desired item and press Enter. | |
| | | |
| | hdisk3 Current=Optimized Preferred=Non Optimized | |
| | hdisk4 Current=Non Optimized Preferred=Non Optimized | |
| | hdisk5 Current=Optimized Preferred=Optimized | |
| | hdisk6 Current=Optimized Preferred=Optimized | |
| | | |
| | F1=Help F2=Refresh F3=Cancel | |
| | F8=Image F10=Exit Enter=Do | |
|F1| /=Find n=Find Next | |
|F9+--------------------------------------------------------------------------+ |
+---------------------------------------------------------------------------------+This display shows the HA access characteristics for the disk arrays with respect to the controller that was selected. For each disk array listed, the current and preferred HA access characteristics are indicated. The current value shows how the disk array is currently accessed from the controller that was selected. The preferred value is the desired access state that is saved with the disk array configuration. Selecting the remote controller would show the opposite settings for the current and preferred access states.
The following access state settings are valid.
- Optimized
- The selected controller performs direct access for this disk array. This gives I/O operations that are performed on selected controller optimized performance compared to the remote controller.
- Non Optimized
- The selected controller performs indirect access for this disk array. This gives I/O operations that are performed on selected controller nonoptimized performance compared to the remote controller.
- Cleared
- Neither an Optimized nor Non Optimized access state has been set for this disk array. By default the disk array is optimized on the primary controller.
The HA access characteristic can be displayed on either the primary or secondary controller. However, as with all other disk array management, the HA access characteristics can only be changed from the primary controller. Setting the preferred HA access characteristic is accomplished by selecting one of the disk arrays. This will bring up the Change/Show HA Access Characteristics of a SAS Disk Array screen. The Preferred Access state can be changed when the disk array is selected from the primary controller. The Preferred Access state cannot be changed if the disk array is selected from the secondary controller. If this is attempted, an error message is displayed. Changing the Preferred Access state from the primary controller stores the settings in the disk array and automatically shows the opposite settings when viewed from the secondary controller.
+---------------------------------------------------------------------------------+
| Change/Show HA Access Characteristics of a SAS Disk Array |
| |
|Type or select values in entry fields. |
|Press Enter AFTER making all desired changes. |
| |
| [Entry Fields] |
| Disk Array hdisk4 |
| Controller sissas0 |
| Current Access Optimized |
| Preferred Access Cleared + |
| |
|F1=Help F2=Refresh F3=Cancel F4=List |
|F5=Reset F6=Command F7=Edit F8=Image |
|F9=Shell F10=Exit Enter=Do |
+---------------------------------------------------------------------------------+The controller always tries to switch the Current Access state of the disk array to match the Preferred Access state. This switching is done in the background by the controller; therefore, you might experience delays between setting the Preferred Access state and seeing Current Access state switch. The delay can be minutes before the switch occurs, especially on caching adapters that need to flush cache before the Current Access state can switch. Situations in which the controller does not switch HA access characteristics involve configuration errors, failed components, and certain RAID configuration activities.
By default all disk arrays are created with a Preferred Access
state of Cleared. To maximize performance, when appropriate,
create multiple disk arrays and optimize them equally between the
controller pair. This is accomplished by setting the Preferred Access
to Optimized for half of the disk arrays and Non
Optimized to the other half.
The HA access characteristics can also be altered by the Preferred HA Access State Setting in the Change/Show SAS RAID controller screen. This field gives the option to either Preserve or Clear the Preferred Access settings for all disk arrays on the controller pair.