Low Throughput and High Latency

Adjusting the RAID Level and RAID Parameters

1. During server startup, press Ctrl + R when the Press <Ctrl><R> to Run MegaRAID Configuration Utility message shown in Figure 3 is displayed. The SAS3108 BIOS Configuration Utility screen is displayed. Table 1 describes the tabs.
   Figure 1 BIOS configuration screen
   

   Table 1 Tab description

   Tab	Description
   VD Mgmt	Manages virtual drives.
   PD Mgmt	Manages physical drives.
   Ctrl Mgmt	Manages RAID controller cards.
   Properties	Queries the RAID controller card properties.
   Foreign View	Manages foreign configurations. This tab is available only when foreign configurations are detected.

2. Go to the Create Virtual Driver page. See Figure 2.
   1. Press Ctrl+P or Ctrl+N to switch to the VD Mgmt tab.
   2. Select SAS3108 (Bus 0x01, Dev 0x00) by pressing ↑ and ↓.
   3. Press F2. On the page that is displayed, select Create Virtual Driver, and press Enter.
   Figure 2 Configuration page
   
3. Configure the RAID level.
   1. Press Enter in the RAID Level area, and use ↑ or ↓ to select the RAID level RAID-0.
      

      • This step is optional for RAID 0, RAID 1, RAID 5, and RAID 6.
      • This step is mandatory for RAID 10, RAID 50, and RAID 60.
   2. Press ↓ to move the mouse pointer to the PD per Span text box.
   3. Set the number of drives for each RAID span.
4. Add drives.
   1. Press ↓ to move the mouse pointer to Drives.
   2. Press ↑ and ↓ to select a drive for the RAID group and press Enter.
   

   [X] is displayed in the ID column for a selected drive.

   

5. Set the RAID capacity and name.
   1. Enter the virtual drive capacity in the Size text box.
      

      • If multiple virtual drives are not required, go to 7 after setting the virtual drive name. The RAID capacity will be the maximum value by default.
      • To divide a drive group into multiple virtual drives, you need to manually configure the capacity for each virtual drive. Each drive group supports a maximum of 16 virtual drives.
   2. Press ↓ to move the mouse pointer to the Name area, set the RAID name, and select OK.
   3. In the confirmation dialog box that is displayed, click OK and press Enter to return to the VD Mgmt page.
6. (Optional) Create multiple virtual drives.
   1. After the drive group is created, select Drive Group on the VD Mgmt page and press F2. In the displayed list, choose Add New VD. The Add VD in Drive Group page is displayed.
   2. Set the VD capacity in Size. Choose OK and press Enter. The confirmation screen is displayed.
   3. Choose OK and press Enter to return to the VD Mgmt page. The VD is created.
7. Configure advanced settings.
   1. Press ↓ and select Advanced. Press Enter. See Figure 3.
      Figure 3 Advanced settings
      

      Table 2 describes the parameters of advanced properties.

      Table 2 Parameters of advanced properties

      Parameter	Description
      Strip Size	Size of a data strip on each drive. The options for LSI SAS3108 include 64 KB, 128 KB, 256 KB, 512 KB, and 1 MB. Generally, the default value 256KB is used during RAID configuration.
      Read Policy	Read policy of a virtual drive. Normal: disables the read ahead function. Ahead: enables the read ahead function. The RAID controller card prefetches sequential data or the data predicted to be used and stores it in the cache.
      Write Policy	Write policy of a virtual drive. The write policy of virtual drives varies with the firmware version of the LSI SAS3108. If the firmware version of the LSI SAS3108 RAID controller card is 4.270.00-4382 or earlier, the following three write policies are supported: Write Back: When the cache receives all data, the RAID controller card signals the host that the data transmission is complete. Write Through: When the drive subsystem receives all data, the RAID controller card signals the host that the data transmission is complete. Write Back with BBU: The RAID controller card automatically switches to the Write Through mode when the RAID controller card has no Battery Backup Unit (BBU), the BBU is on charge or discharge, the BBU is faulty, or the Pinned/Preserved cache reaches 50% of the physical cache. This mode is recommended. If the firmware version of the LSI SAS3108 RAID controller card is 4.650.00-6121 or later, the following three write policies are supported: Write Back: The RAID controller card automatically switches to the Write Through mode when the RAID controller card has no BBU, the BBU is on charge or discharge, the BBU is faulty, or the Pinned/Preserved cache reaches 50% of the physical cache. This mode is recommended. Write Through: When the drive subsystem receives all data, the RAID controller card signals the host that the data transmission is complete. Always Write Back: When the cache receives all data, the RAID controller card signals the host that the data transmission is complete. NOTE: In Always Write Back mode, DDR write data of the RAID controller card will be lost if the supercapacitor is not installed or being charged. This mode is not recommended.
      I/O Policy	Options for data I/O of special virtual drives. This policy does not affect cache prefetch. The options are: Direct In a read scenario, data is directly read from drives. (If Read Policy is set to Ahead, data is read from the RAID cache.) In a write scenario, data is written into the RAID cache. (If Write Policy is set to Write Through, data is directly written into drives.) Cached: Data is read from or written into the cache. Use this option only when configuring CacheCade 1.1.
      Disk cache Policy	Cache policy for physical drives. Enable: writes data to the cache before writing data to the drive. This option improves data write performance. However, data will be lost if there is no protection mechanism against power failures. Disable: writes data to a drive without caching the data. Data is not lost if power failures occur. Unchanged: uses the current cache policy.
      Emulation	Sets the virtual sector size. NOTE: This parameter is supported when the firmware version of the LSI SAS3108 RAID controller card is 4.660.00-8102 or later.
      Initialize	Performs initialization once a RAID array is created. The initialization will damage data stored on RAID member drives. It is marked by [X] after selected.
      Configure HotSpare	Configures hot spare drives for a RAID array. It is marked by [X] after selected. This parameter is invalid if you create a RAID 0 array.
      Disable BGI	Disables background initialization. NOTE: This parameter is supported when the firmware version of the LSI SAS3108 RAID controller card is 4.660.00-8102 or later.

   2. Set the advanced RAID properties as required.
      

      Initialization will damage data on drives. If the original data on the drives needs to be retained, do not select Initialize.

   3. Choose OK and press Enter to return to the Create New VD page. If Initialize is selected, a confirmation dialog box is displayed when the initialization is complete. Press Enter to return to the main screen.
8. Check the configuration result.

   On the CU main screen, press → to expand information, and view the detailed configurations.

   

9. Press Esc to exit the CU configuration page and restart the server.