IBM-AUSTRIA - PC-HW-Support    30 Aug 1999

Using the ServeRAID GUI-Based Configuration CD

To start the configuration program:

1.  Insert the ServeRAID GUI-Based CD into the  CD-ROM drive, then, turn on the server.

    One of the following screens will appear:  

   •  If the configuration program detects unconfigured  ServeRAID controllers, the program starts in the Configuration mode and  a screen similar to the following appears.
      
      Select the Cancel button to switch from the Configuration mode to the  Information mode.
   •  If the configuration program detects that all  ServeRAID adapters and controllers in the server are configured, the  program starts in the Information mode and a screen similar to the  following appears.
      
      Select the

      
      icon on the Tool Bar to switch from the Information mode to  the Configuration mode.  

2.  Change Write-Cache Mode to Write-Through or  Write-Back:

    This choice is available in the Information mode when  you select a specific logical drive icon from the Main Tree.

    When this feature is set to the write-through mode, the completion  status of a write command is sent after  the data is written to the hard  disk drive. Under certain workloads, you can improve performance by  changing this setting to the write-back mode, where the completion  status of a write command is sent after  the data is copied to cache  memory, but before  the data is actually written to the storage device.

     -Attention-

   1.  You might lose data if a power outage  occurs while using the write-back mode without a Battery-Backup Cache  device.
   2.  If you do not have a Battery-Backup Cache  installed and Enabled and you set this feature to the write-back mode,  wait at least 10 seconds after your last operation before you turn off  your system. Failure to follow this practice can result in lost data.
3.  Disable or Enable Read-Ahead Cache Mode:

    This choice is available in the Information mode only. When read-ahead cache  is set to Enabled  (default setting), the ServeRAID controller transfers  data from a disk to its local cache in increments equal to the stripe  unit size. This provides excellent overall performance when workloads  are steady and sequential.

    However, if the workload is random or the  system I/O requests are smaller than the stripe unit size, reading ahead  to the end of the stripe might degrade performance. When read-ahead  cache is set to Disabled , the ServeRAID controller transfers data from a  disk to local cache in increments equal to the system I/O request size,  without reading ahead to the end of the stripe.

4.  Change the Rebuild Rate:

    This choice is available   in the Information mode only. You can select this choice to set the  priority for Rebuild operations to High  (default), Medium , or Low .  

   •  When the rebuild rate is set to High , the rebuild  I/O request gets high priority in the execution order.
   •  When the rebuild request is set from High  to Medium  in a heavily-loaded system, it can  increase the rebuild time, but provide better system performance.
   •  When the rebuild request is set from High  or Medium  to Low  in a moderately- to heavily-loaded system, it can increase  the disk rebuild time, but provides better system performance.  

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