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RAID Configuration and Management

Dell™ PowerEdge™ Expandable RAID Controller 4/Di/Si and 4e/Di/Si User's Guide

  Entering the BIOS Configuration Utility

  Exiting the Configuration Utility

  RAID Configuration Functions

  Configuration Utility Menu

  BIOS Configuration Utility Menu Options

  Device Management

  Simple Array Setup

  Advanced Array Setup

  Managing Arrays

  Deleting Logical Drives

  Patrol Read

This section describes how to configure physical drives into arrays and logical drives using the BIOS Configuration Utility. Your PERC controller can also be configured using the Dell OpenManage Array or Dell OpenManage Storage Management applications. See RAID Management Utilities in Features for information about the OpenManage applications.

Entering the BIOS Configuration Utility

The BIOS Configuration Utility configures disk arrays and logical drives. Because the utility resides in the RAID controller BIOS, its operation is independent of the operating systems on your system.

Starting the BIOS Configuration Utility

When the host computer boots, hold the <Ctrl> key and press the <M> key when a BIOS banner similar to the following displays (the text for the BIOS banner may vary slightly between controllers and BIOS versions):

HA -0 (Bus X Dev X) Type: PERC 4e/Di Standard FWx.xx SDRAM=xxx MB

Battery Module is Present on Adapter

1 Logical Drive found on the Host Adapter

Adapter BIOS Disabled, No Logical Drives handled by BIOS

0 Logical Drive(s) handled by BIOS

Press <Ctrl><M> to Enable BIOS

For each controller in the host system, the firmware version, dynamic random access memory (DRAM) size, and the status of logical drives on that controller display. After you press a key to continue, the Management Menu screen displays.

NOTE: In the BIOS Configuration Utility, pressing <Ctrl><M> has the same effect as pressing <Enter>.

NOTE: You can access multiple controllers through the BIOS Configuration Utility. Be sure to verify which controller you are currently set to edit.

Exiting the Configuration Utility

1. Press <Esc> when the Management Menu displays.
   
   
2. Select Yes at the prompt.
   
   
3. Reboot the system.
   
   

RAID Configuration Functions

NOTE: The OpenManage™ Array Manager and Dell OpenManage Storage Management can perform many of the same tasks as the BIOS Configuration Utility.

After you have attached all physical drives, use a configuration utility to prepare a logical drive. Your SCSI hard drives must be organized into logical drives in an array and be able to support the RAID level that you select. If the operating system is not yet installed, use the BIOS Configuration Utility to perform this procedure. If the operating system is installed, you can use OpenManage Array Manager (for Windows and NetWare) or Dell OpenManage Storage Management.

Use the configuration utilities to perform the following tasks:

• Configure physical arrays and logical drives.
  
  
• Create hot spare drives.
  
  
• Initialize one or more logical drives.
  
  
• Access controllers, logical drives, and, physical drives individually.
  
  
• Rebuild failed hard drives.
  
  
• Verify that the redundancy data in logical drives using RAID level 1, 5, 10, or 50 is correct.
  
  
• Reconstruct logical drives after changing RAID levels or adding a hard drive to an array.
  
  
• Select a host controller to work on.
  
  

The following sections describe the menu options and provide detailed instructions used to perform the configuration tasks. The following is a list of the procedures used to configure hard disk drives into arrays and logical drives. They apply to the BIOS Configuration Utility, OpenManage Array Manager, and Dell OpenManage Storage Management. The following is a list of the configuration steps:

1. Designate hot spares (optional).
   
   

See Designating Drives as Hot Spares in this section for more information.

2. Select a configuration method.
   
   

See Configure Menu for more information.

3. Create arrays using the available physical drives.
   
   
4. Define logical drives using the arrays.
   
   
5. Save the configuration information.
   
   
6. Initialize the logical drives.
   
   

See Simple Array Setup and Advanced Array Setup for the detailed configuration procedures.

Configuration Utility Menu

Figure 4-1 shows the menu tree for the BIOS Configuration Utility. The following sections describe each menu item.

Figure 4-1. BIOS Configuration Utility Menu Tree

BIOS Configuration Utility Menu Options

Table 4-1 describes the options for the BIOS Configuration Utility Management Menu. The menu and sub-menu options are explained in the following sections.

Table 4-1. BIOS Configuration Utility Menu Options  

Configure Menu

Select Configure to select a method for configuring arrays and logical drives. Table 4-2 displays the configuration methods, clear configuration option, and boot drive option.

Table 4-2. Configuration Menu Options 

Initialize Menu

NOTE: See Simple Array Setup or Advanced Array Setup for steps for initializing logical drives.

Select Initialize from the Management Menu to initialize one or more logical drives. Press the space bar to select a single drive or the <F2> key to select all drives for initialization. This action typically follows the configuration of a new logical drive.

NOTICE: Initializing a logical drive destroys all data on the logical drive.

Objects Menu

Select Objects from the Management Menu to access the adapters, logical drives, physical drives, and SCSI channels individually. You can also change settings for each object. The Objects menu options are described in the following sections.

Adapter

Select Objects→ Adapter to select a controller (if the computer has more than one) and to modify parameters. Table 4-3 describes the Adapter menu options.

Table 4-3. Adapter Menu Options 

Patrol Read Options

Table 4-4 describes the Patrol Read Options submenu. See Patrol Read for detailed information about the Patrol Read.

Table 4-4. Patrol Read Options Menu 

Logical Drive

Select Objects→ Logical Drive to select a logical drive and to perform the actions listed in Table 4-5.

Table 4-5. Logical Drive Menu Options 

Physical Drive

Select Objects→ Physical Drive to select a physical device and to perform the operations listed in the table below. The physical drives in the computer are listed. Move the cursor to the desired device and press <Enter> to display the screen.

Table 4-6 displays the operations you can perform on the physical drives.

Table 4-6. Physical Drive Menu Options 

Channel

Select Objects→ Channel to select a SCSI channel on the currently selected controller. After you select a channel, press <Enter> to display the options for that channel. Table 4-7 describes the SCSI channel menu options.

Table 4-7. SCSI Channel Menu Options 

Clear Menu

You can clear the data from SCSI drives using the configuration utilities. See Clearing Physical Drives for more information and the procedure for clearing the data.

Rebuild Menu

Select Rebuild from the Management Menu to rebuild one or more failed physical drives. See Rebuilding Failed Hard Drives for more information and the procedure to perform a drive rebuild.

Check Consistency Menu

Select Check Consistency to verify the redundancy data in logical drives that use RAID levels 1, 5, 10, and 50. See Checking Data Consistency for more information and the procedure to perform a check consistency.

Reconstruct Menu

Select Reconstruct to change the RAID level of an array or add a physical drive to an existing array. RAID level migration changes the array from one RAID level to another. Online capacity expansion is the addition of hard disk drives to increase storage capacity.

Device Management

Device Management Functions

This section deals with device management, which means management of the physical devices. This includes the physical drives, hot spares, drive migration, and drive roaming. See Drive Roaming and Drive Migration for details about these procedures.

Physical Drive Selection Menu

The configuration utility offers the Physical Drive Selection Menu which you can use to perform actions on the physical drives in an array, such as rebuilding a drive or making a hot spare online or offline. Some of these actions are described in detail in other sections of this chapter. Perform the following steps to view the actions you can select.

1. On the Management Menu select Objects—> Physical Drive.
   
   

A physical drive selection screen appears.

2. Select a hard drive in the READY state and press <Enter> to display the action menu for the physical drives.
   
   

The menu items are:

• Rebuild
  
  
• Clear
  
  
• Force Online
  
  
• Force Offline/Remove HSP
  
  
• Make HotSpare
  
  
• View Drive Information
  
  
• View Rebuild Progress
  
  
• SCSI Command Qtagging
  
  
• Set Write Cache
  
  
• Transfer Speed Option
  
  

Device Configuration

You can fill in the following table to list the devices assigned to Channel 1. The PERC 4/Si and 4e/Si controllers have one channel, and the PERC 4/Di and 4e/Di have two.

Use Table 4-8 to list the devices that you assign to each SCSI ID for SCSI Channel 1.

Table 4-8. Configuration for SCSI Channel 1 

Simple Array Setup

This section describes the steps used in Easy Configuration to set up a simple array and create logical drives. In Easy Configuration, each physical array you create is associated with exactly one logical drive, so you cannot span arrays. In addition, in Easy Configuration, you cannot change the logical drive size.

You can modify the following logical drive parameters, which are described in Table 4-9. The spanning option is also described in Table 4-9, though you cannot span arrays using Easy Configuration.

• RAID level
  
  
• Stripe size
  
  
• Write policy
  
  
• Read policy
  
  
• Cache policy
  
  

Table 4-9. Logical Drive Parameters and Descriptions 

If logical drives have already been configured when you select Easy Configuration, the configuration information is not disturbed. Perform the following steps to create arrays and logical drives using Easy Configuration.

1. Select Configure—> Easy Configuration from the Management Menu.
   
   

Hot key information displays at the bottom of the screen.

2. Press the arrow keys to highlight specific physical drives.
   
   
3. Press the spacebar to associate the selected physical drive with the current array.
   
   

The selected drive changes from READY to ONLIN A[array number]-[drive number]. For example, ONLIN A02-03 means array 2 with hard drive 3.

4. Add physical drives to the current array as desired.
   
   

Try to use drives of the same capacity in a specific array. If you use drives with different capacities in an array, all drives in the array are treated as if they have the capacity of the smallest drive in the array.

NOTE: When you create a logical drive, you can select more than 2 TB of physical hard drive space, but 2 TB is the largest logical drive you can create. After you select the physical drives, you are prompted to press <Enter> to accept the 2TB logical drive size. You are then prompted to accept the next logical drive, which will be the remaining amount of physical hard drive space.

5. Press <Enter> after you finish creating the current array.
   
   

The Select Configurable Array(s) window appears. It displays the array and array number, such as A-00.

6. Press the spacebar to select the array.
   
   

NOTE: You can press <F2> to display the number of drives in the array, their channel and ID, and press <F3> to display array information, such as the stripes, slots, and free space.

7. Press <F4> to add a hotspare, if desired, and select Yes at the prompt.
   
   

See Designating Drives as Hot Spares for more information.

8. Press <F10> to configure a logical drive.
   
   

The window at the top of the screen shows the logical drive that is currently being configured.

9. Highlight RAID and press <Enter> to set the RAID level for the logical drive.
   
   

The available RAID levels for the current logical drive display.

10. Select a RAID level and press <Enter> to confirm.
    
    
11. Click Advanced Menu to open the menu for logical drive settings.
    
    
12. Set the Stripe Size.
    
    
13. Set the Write Policy.
    
    
14. Set the Read Policy.
    
    
15. Set the Cache Policy.
    
    
16. Press <Esc> to exit the Advanced Menu.
    
    
17. After you define the current logical drive, select Accept and press <Enter>.
    
    

The array selection screen appears if any unconfigured hard drives remain.

18. Repeat step 2 through step 17 to configure another array and logical drive.
    
    

The RAID controller supports up to 40 logical drives per controller.

19. When finished configuring logical drives, press <Esc> to exit Easy Configuration.
    
    

A list of the currently configured logical drives appears.

20. Respond to the Save prompt.
    
    

After you respond to the prompt, the Configure menu appears.

21. Press <Esc> to return to the Management Menu.
    
    

The logical drives you configured need to be initialized to prepare them for use.

22. Select Initialize on the Management Menu.
    
    

The configured logical drives display.

NOTE: When the Fast Initialization option in the Objects→ Adapter menu is set to Disabled, a full initialization takes place on the entire logical drive. On a larger array (over 5 arrays), it is best to set fast initialization to Disabled, then initialize. Otherwise, the controller will run a background consistency check within five minutes of reboot or RAID 5 creation.

NOTE: A full initialization will not resume after a power loss; it will start completely over.

23. Use the arrow key to highlight a logical drive, then press the spacebar to select a logical drive or press<F2> to select all the logical drives.
    
    
24. Press <F10> to initialize the selected logical drive(s) and select Yes at the prompt.
    
    

A progress bar displays.

25. When the initialization is complete, press <Esc> to return to the Management Menu.
    
    

Advanced Array Setup

The following procedures describe more advanced array and logical drive setups. The difference between simple setup and advanced setup is that you can select drive size and span arrays in advanced setup. The configuration utilities offer New Configuration and View/Add Configuration options, which are described in the following procedures.

Using New Configuration

If you select New Configuration, the existing configuration information on the selected controller is destroyed when the new configuration is saved. In New Configuration, you can modify the following logical drive parameters:

• RAID level
  
  
• Logical drive size
  
  
• Stripe size
  
  
• Write policy
  
  
• Read policy
  
  
• Cache policy
  
  
• Spanning of arrays
  
  

NOTICE: Selecting New Configuration erases the existing configuration information on the selected controller. To use the existing configuration, use View/Add Configuration.

1. Select Configure—> New Configuration from the Management Menu.
   
   

Hot key information appears at the bottom of the screen.

2. Press the arrow keys to highlight specific physical drives.
   
   
3. Press the spacebar to associate the selected physical drive with the current array.
   
   

The selected drive changes from READY to ONLINE A[array number]-[drive number]. For example, ONLINE A02-03 means array 2 with hard drive 3.

4. Add physical drives to the current array as desired.
   
   

Try to use drives of the same capacity in a specific array. If you use drives with different capacities in an array, all drives in the array are treated as if they have the capacity of the smallest drive in the array.

NOTE: When you create a logical drive, you can select more than 2 TB of physical hard drive space, but 2 TB is the largest logical drive you can create. After you select the physical drives, you are prompted to press <Enter> to accept the 2TB logical drive size. You are then prompted to accept the next logical drive, which will be the remaining amount of physical hard drive space.

5. Press <Enter> twice after you finish creating the current array.
   
   

The Select Configurable Array(s) window appears. It displays the array and array number, such as A-00.

6. Press the spacebar to select the array.
   
   

Span information displays in the array box. You can create multiple arrays, then select them to span them.

NOTE: You can press <F2> to display the number of drives in the array, their channel and ID, and <F3> to display array information, such as the stripes, slots, and free space.

7. Repeat step 2 through step 6 to create another array or go to step 8 to configure a logical drive.
   
   
8. Press <F10> to configure a logical drive.
   
   

The logical drive configuration screen appears. Span=Yes displays on this screen if you select two or more arrays to span.

The window at the top of the screen shows the logical drive that is currently being configured as well as any existing logical drives.

9. Highlight RAID and press <Enter> to set the RAID level for the logical drive.
   
   

A list of the available RAID levels for the current logical drive appears.

10. Select a RAID level and press <Enter> to confirm.
    
    
11. Highlight Span and press <Enter>.
    
    

NOTE: Make sure that the spans are in different backplanes, so that if one span fails, you won't lose the whole array.

12. Highlight a spanning option and press <Enter>.
    
    
13. Move the cursor to Size and press <Enter> to set the logical drive size.
    
    

By default, the logical drive size is set to all available space in the array(s) being associated with the current logical drive, accounting for the Span setting.

14. Click Advanced Menu to open the menu for logical drive settings.
    
    
15. Set the Stripe Size.
    
    
16. Set the Write Policy.
    
    
17. Set the Read Policy.
    
    
18. Set the Cache Policy.
    
    
19. Press <Esc> to exit the Advanced Menu.
    
    
20. After you define the current logical drive, select Accept and press <Enter>.
    
    

If space remains in the arrays, the next logical drive to be configured appears. If the array space has been used, a list of the existing logical drives appears.

21. Press any key to continue, then respond to the Save prompt.
    
    
22. Press <Esc> to return to the Management Menu.
    
    

The logical drives you configured need to be initialized to prepare them for use.

23. Select Initialize on the Management Menu.
    
    

The configured logical drives display.

NOTE: A full initialization will not resume after a power loss; it will start completely over.

24. Use the arrow key to highlight a logical drive, then press the spacebar to select a logical drive or press<F2> to select all the logical drives.
    
    
25. Press <F10> to initialize the selected logical drive(s) and select Yes at the prompt.
    
    

A progress bar displays.

26. When the initialization is complete, press <Esc> to return to the Management Menu.
    
    

Using View/Add Configuration

View/Add Configuration allows you to control the same logical drive parameters as New Configuration without disturbing the existing configuration information. In addition, you can enable the Configuration on Disk feature.

1. Select Configure—> View/Add Configuration from the Management Menu.
   
   

Hot key information appears at the bottom of the screen.

2. Press the arrow keys to highlight specific physical drives.
   
   
3. Press the spacebar to associate the selected physical drive with the current array.
   
   

The selected drive changes from READY to ONLIN A[array number]-[drive number]. For example, ONLIN A02-03 means array 2 with hard drive 3.

4. Add physical drives to the current array as desired.
   
   

Try to use drives of the same capacity in a specific array. If you use drives with different capacities in an array, all drives in the array are treated as if they have the capacity of the smallest drive in the array.

NOTE: When you create a logical drive, you can select more than 2 TB of physical hard drive space, but 2 TB is the largest logical drive you can create. After you select the physical drives, you are prompted to press <Enter> to accept the 2TB logical drive size. You are then prompted to accept the next logical drive, which will be the remaining amount of physical hard drive space.

5. Press <Enter> twice after you finish creating the current array.
   
   

The Select Configurable Array(s) window appears. It displays the array and array number, such as A-00.

6. Press the spacebar to select the array.
   
   

Span information, such as Span-1, displays in the array box. You can create multiple arrays, then select them to span them.

NOTE: You can press <F2> to display the number of drives in the array, their channel and ID, and <F3> to display array information, such as the stripes, slots, and free space.

7. Press <F10> to configure a logical drive.
   
   

The logical drive configuration screen appears. Span=Yes displays on this screen if you select two or more arrays to span.

8. Highlight RAID and press <Enter> to set the RAID level for the logical drive.
   
   

The available RAID levels for the current logical drive appear.

9. Select a RAID level and press <Enter> to confirm.
   
   
10. Highlight Span and press <Enter>.
    
    
11. Highlight a spanning option and press <Enter>.
    
    

The maximum number of spans is eight.

12. Move the cursor to Size and press <Enter> to set the logical drive size.
    
    

By default, the logical drive size is set to all available space in the array(s) associated with the current logical drive, accounting for the Span setting.

13. Highlight Span and press <Enter>.
    
    
14. Highlight a spanning option and press <Enter>.
    
    

NOTE: The full drive size is used when you span logical drives; you cannot specify a smaller drive size.

15. Click Advanced Menu to open the menu for logical drive settings.
    
    
16. Set the Stripe Size.
    
    
17. Set the Write Policy.
    
    
18. Set the Read Policy.
    
    
19. Set the Cache Policy.
    
    
20. Press <Esc> to exit the Advanced Menu.
    
    
21. After you define the current logical drive, select Accept and press <Enter>.
    
    

If space remains in the arrays, the next logical drive to be configured appears.

22. Repeat step 2 to step 21 to create an array and configure another logical drive.
    
    

If all array space is used, a list of the existing logical drives appears.

23. Press any key to continue, then respond to the Save prompt.
    
    
24. Press <Esc> to return to the Management Menu.
    
    

The logical drives you configured need to be initialized to prepare them for use.

25. Select Initialize on the Management Menu.
    
    

The configured logical drives display.

NOTE: A full initialization will not resume after a power loss; it will start completely over.

26. Use the arrow key to highlight a logical drive, then press the spacebar to select a logical drive or press<F2> to select all the logical drives.
    
    
27. Press <F10> to initialize the selected logical drive(s) and select Yes at the prompt.
    
    

A progress bar displays.

28. When the initialization is complete, press <Esc> to return to the Management Menu.
    
    

Managing Arrays

Your SCSI hard drives must be organized into logical drives in an array and must be able to support the RAID level that you select. This section describes:

• Guidelines for connecting and configuring SCSI devices in a RAID array
  
  
• Storage space in RAID 1 and RAID 5 arrays with hard disk drives of different sizes
  
  
• Maximum number of hard disk drives that you can use in each RAID level
  
  
• Array configuration
  
  
• Logical drive properties
  
  
• Clearing physical drives
  
  
• Designating physical drives as hot spares
  
  
• Rebuilding failed physical drives
  
  
• Checking data consistency
  
  
• Reconstructing logical drives
  
  
• Performing an online capacity expansion
  
  
• Performing drive roaming or drive migration
  
  

Guidelines for SCSI Devices in a RAID Array

Observe the following guidelines when connecting and configuring SCSI devices in a RAID array:

• Consider the number of hard disk drives in the array when deciding on the RAID level to use. See RAID Levels for the number of drives supported for each array level.
  
  
• Use drives of the same size and speed to maximize the effectiveness of the controller.
  
  
• When replacing a failed drive in a redundant array, make sure that the replacement drive has the same or larger capacity than the smallest drive in the array (RAID 1, 5, 10, and 50).
  
  

When implementing RAID 1 or RAID 5, disk space is spanned to create the stripes and mirrors. The span size can vary to accommodate the different disk sizes. There is, however, the possibility that a portion of the largest disk in the array will be unusable, resulting in wasted disk space. For example, consider a RAID 1 array that has the following disks, as shown in Table 4-10.

Table 4-10. Storage Space in a RAID 1 Array

In the RAID 1 example, data is mirrored across the two disks until 20 GB on Disk A and B are completely full. This leaves 10 GB of disk space on Disk B. Data cannot be written to this remaining disk space, as there is no corresponding disk space available in the array to create redundant data.

Table 4-11 provides an example of a RAID 5 array.

Table 4-11. Storage Space in a RAID 5 Array

In the RAID 5 example, data is striped across the disks until 40 GB on Disks A, B, and C are completely full. This leaves 20 GB of disk space on Disk C. Data cannot be written to this remaining disk space, as there is no corresponding disk space available in the array to create redundant data.

RAID levels 10 and 50 span RAID 1 and RAID 5 arrays, respectively. When one array fills its available storage space, the other array(s) may have additional storage space available. You can still use fill the additional available space in the larger array(s). Because there is additional storage space in the larger array(s), you can use arrays of different sizes without having to leave storage space unused. See Storage in RAID 10 and RAID 50 Arrays for more information about storage space in RAID 10 and 50 arrays.

Assigning RAID Levels

Only one RAID level can be assigned to each logical drive. Table 4-12 shows the minimum and maximum number of drives required for each RAID level.

Table 4-12. Physical Drives Required for Each RAID Level 

Array Configuration

After you configure and initialize the hard drives, you are ready to configure arrays. The number of drives in an array determines the RAID levels that can be supported. For information about the number of drives required for different RAID levels, see Table 4-12 in Assigning RAID Levels.

Logical Drives

Logical drives, also known as virtual disks, are arrays or spanned arrays that are available to the operating system. The storage space in a logical drive is spread across all the physical drives in the array or spanned arrays.

You must create one or more logical drives for each array, and the logical drive capacity must include all of the drive space in an array. You can make the logical drive capacity larger by spanning arrays. In an array of drives with mixed sizes, the smallest common drive size is used and the space in larger drives is not used. The RAID controller supports up to 40 logical drives.

Configuring Logical Drives

After you have attached all physical drives, perform the following steps to prepare a logical drive. If the operating system is not yet installed, use the BIOS Configuration Utility to perform this procedure.

1. Start the system.
   
   
2. Run your array management software.
   
   
3. Select the option to customize the RAID array.
   
   

In the BIOS Configuration Utility, use either Easy Configuration or New Configuration to customize the RAID array.

CAUTION: If you select New Configuration, all previous configuration information will be deleted.

4. Create and configure one or more system drives (logical drives).
   
   
5. Select the RAID level, cache policy, read policy, and write policy.
   
   

NOTE: Refer to the section Summary of RAID Levels for RAID level explanations and Table 4-9 for information about the policy settings.

6. Save the configuration.
   
   
7. Initialize the system drives.
   
   

After initialization, you can install the operating system.

NOTE: A full initialization will not resume after a power loss; it will start completely over.

See Simple Array Setup and Advanced Array Setup for detailed configuration instructions.

Spanned Drives

You can arrange arrays sequentially with an identical number of drives so that the drives in the different arrays are spanned. Spanned drives can be treated as one large drive. Data can be striped across multiple arrays as one logical drive. The maximum number of spans is eight.

You can create spanned drives using your array management software, which is the BIOS Configuration Utility.

Storage in an Array with Drives of Different Sizes

For RAID levels 0 and 5, data is striped across the disks. If the hard drives in an array are not the same size, data is striped across all the drives until one or more of the drives is full. After one or more drives are full, disk space left on the other disks cannot be used. Data cannot be written to that disk space because other drives do not have corresponding disk space available.

Figure 4-2 shows an example of storage allocation in a RAID 5 array. The data is striped, with parity, across the three drives until the smallest drive is full. The remaining storage space in the other hard drives cannot be used because not all of the drives have disk space for redundant data.

NOTE: Using hard disk drives of different sizes is not recommended.

Figure 4-2. Storage in a RAID 5 Array

Storage in RAID 10 and RAID 50 Arrays

You can span RAID 1 and 5 arrays to create RAID 10 and RAID 50 arrays, respectively. For RAID levels 10 and 50, you can have some arrays with more storage space than others. After the storage space in the smaller arrays is full, you can use the additional space in larger arrays can store data.

Figure 4-3 shows the example of a RAID 50 span with three RAID 5 arrays of different sizes. (Each array can have from three to 14 hard disks.) Data is striped across the three RAID 5 arrays until the smallest array is full. The data is striped across the remaining two RAID 5 arrays until the smaller of the two arrays is full. Finally, data is stored in the additional space in the largest array.

Figure 4-3. Storage in a RAID 50 Array

Performance Considerations

The system performance improves as the number of spans increases. As the storage space in the spans is filled, the system stripes data over fewer and fewer spans and RAID performance degrades to that of a RAID 1 or RAID 5 array.

Clearing Physical Drives

You can clear the data from SCSI drives using the configuration utilities. To clear a drive, perform the following steps:

1. Select Management Menu—> Objects—> Physical Drives in the BIOS Configuration Utility.
   
   

A device selection window displays the devices connected to the current controller.

2. Press the arrow keys to select the physical drive to be cleared and press <Enter>.
   
   
3. Select Clear.
   
   
4. When clearing completes, press any key to display the previous menu.
   
   

NOTICE: Do not terminate the clearing process, as it makes the drive unusable. You would have to clear the drive again before you could use it.

Displaying Media Errors

Check the View Drive Information screen for the drive to be formatted. Perform the following steps to display this screen which contains the media errors:

1. Select Objects—> Physical Drives from the Management Menu.
   
   
2. Select a device.
   
   
3. Press <F2>.
   
   

The error count displays at the bottom of the properties screen as they occur. If you feel that the number of errors is excessive, you should probably clear the hard drive. You do not have to select Clear to erase existing information on your SCSI disks, such as a DOS partition. That information is erased when you initialize logical drives.

Designating Drives as Hot Spares

Hot spares are physical drives that are powered up along with the RAID drives and usually stay in a standby state. If a hard drive used in a RAID logical drive fails, a hot spare will automatically take its place and the data on the failed drive is reconstructed on the hot spare. Hot spares can be used for RAID levels 1, 5, 10, and 50. Each controller supports up to eight hot spares.

NOTE: In the BIOS Configuration Utility, only global hot spares can be assigned. Dedicated hot spares cannot be assigned.

The methods for designating physical drives as hot spares are:

• Pressing <F4> while creating arrays in Easy, New or View/Add Configuration mode.
  
  
• Using the Objects—> Physical Drive menu.
  
  

<F4> Key

When you select any configuration option, a list of all physical devices connected to the current controller appears. Perform the following steps to designate a drive as a hot spare:

1. On the Management Menu select Configure, then a configuration option.
   
   
2. Press the arrow keys to highlight a hard drive that displays as READY.
   
   
3. Press <F4> to designate the drive as a hot spare.
   
   
4. Click YES to make the hot spare.
   
   

The drive displays as HOTSP.

5. Save the configuration.
   
   

Objects Menu

1. On the Management Menu select Objects—> Physical Drive.
   
   

A physical drive selection screen appears.

2. Select a hard drive in the READY state and press <Enter> to display the action menu for the drive.
   
   
3. Press the arrow keys to select Make HotSpare and press <Enter>.
   
   

The selected drive displays as HOTSP.

Rebuilding Failed Hard Drives

If a hard drive fails in an array that is configured as a RAID 1, 5, 10, or 50 logical drive, you can recover the lost data by rebuilding the drive with another drive or drives. You can manually rebuild one drive or a group of drives using the manual rebuild procedures in this section.

If a system is rebooted during a rebuild operation, it is possible for the rebuild to restart from 0 percent.

NOTE: An array may take longer to rebuild when under high stress; for example, when there is one rebuild I/O operation to five host I/O operations.

NOTE: In a clustering environment, if a node fails during a rebuild, the rebuild is re-started by another node. The rebuild on the second mode starts at zero percent.

Rebuild Types

Table 4-13 describes automatic and manual rebuilds.

Table 4-13. Rebuild Types

NOTE: If a rebuild to a hotspare fails for any reason, the hotspare drive will be marked as "failed".

Use the following procedures to rebuild one failed drive manually in an individual mode or multiple drives in a batch mode.

Manual Rebuild – Rebuilding an Individual Drive

1. Select Objects—> Physical Drive from the Management Menu.
   
   

A device selection window displays the devices connected to the current controller.

2. Designate an available drive as a hot spare before the rebuild starts.
   
   

See Designating Drives as Hot Spares for instructions on designating a hot spare.

3. Press the arrow keys to select the failed physical drive you want to rebuild, then press <Enter>.
   
   
4. Select Rebuild from the action menu and respond to the confirmation prompt.
   
   

Rebuilding can take some time, depending on the drive capacity.

5. When the rebuild is complete, press any key to display the previous menu.
   
   

Manual Rebuild – Batch Mode

1. Select Rebuild from the Management Menu.
   
   

A device selection window displays the devices connected to the current controller. The failed drives display as FAIL.

2. Press the arrow keys to highlight any failed drives to be rebuilt.
   
   
3. Press the spacebar to select the desired physical drives for rebuild.
   
   
4. After you select the physical drives, press <F10> and select Yes at the prompt.
   
   

The selected drives change to REBLD. Rebuilding can take some time, depending on the number of drives selected and the drive capacities.

5. When the rebuild is complete, press any key to continue.
   
   
6. Press <Esc> to display the Management Menu.
   
   

Checking Data Consistency

Select the Check Consistency option in the configuration utility to verify the redundancy data in logical drives that use RAID levels 1, 5, 10, and 50. (RAID 0 does not provide data redundancy.) The parameters of the existing logical drives appear and discrepancies are automatically corrected when the data is correct. However, if the failure is a read error on a data drive, the bad data block is reassigned and the data is re-generated.

NOTE: Dell recommends that you run data consistency checks on a redundant array at least once a month. This allows detection and automatic replacement of bad blocks. Finding a bad block during a rebuild of a failed drive is a serious problem, as the system does not have the redundancy to recover the data.

NOTE: The system will take longer to reboot after you perform a data consistency check.

Perform the following steps to run Check Consistency:

1. Access the Management Menu.
   
   
2. Select Check Consistency.
   
   
3. Press the arrow keys to highlight the desired logical drives.
   
   
4. Press the spacebar to select or deselect a drive for consistency checking.
   
   
5. Press <F2> to select or deselect all the logical drives.
   
   
6. Press <F10> to begin the consistency check.
   
   

A progress graph for each selected logical drive displays.

7. When the check is finished, press any key to clear the progress display.
   
   
8. Press <Esc> to display the Management Menu.
   
   

(To check an individual drive, select Objects—> Logical Drives from the Management Menu, the desired logical drive(s), then Check Consistency on the action menu.)

NOTE: Stay at the Check Consistency menu until the check is complete.

Reconstructing Logical Drives: RAID Level Migration and Online Capacity Expansion

A reconstruction occurs when you change the RAID level of an array or add a physical drive to an existing array. RAID level migration changes the array from one RAID level to another. Online capacity expansion is the addition of hard disk drives to increase storage capacity. You can perform a reconstruction while the system continues to run, without having to reboot. This avoids downtime and keeps data available to users.

NOTE: After you start the reconstruct process, you must wait until it is complete. Do not reboot, cancel, or exit until the reconstruction is complete.

NOTE: When performing a RAID level migration or an online capacity expansion, a fictional disk may appear in the Windows Disk Management, Dell OpenManage Array Manager, or Dell OpenManage Storage Services application, if the system is rebooted before the process is finished. This disk can be ignored and will disappear once the RAID level migration or online capacity expansion is complete.

Performing a RAID level migration on a clustered system will change the system to non-clustered mode, causing a cluster mismatch error if the system is rebooted.

NOTE: An automatic drive rebuild will not start if you replace a drive during a RAID level migration or an online capacity expansion. The rebuild must be started manually after the expansion or migration procedure is complete.

Perform the following steps to reconstruct a drive:

1. Move the arrow key to highlight Reconstruct on the Management Menu.
   
   
2. Press <Enter>.
   
   

A window entitled "Reconstructables" displays. This contains the logical drives that can be reconstructed. You can press <F2> to view logical drive information or <Enter> to select the reconstruct option.

3. Press <Enter>.
   
   

The next reconstruction window displays. The options on this window are <spacebar> to select or deselect a drive, <Enter> to open the reconstruct menu, and <F3> to display logical drive information.

4. Press <Enter> to open the reconstruct menu.
   
   

The menu items are RAID level, stripe size, and reconstruct.

5. To change the RAID level, select RAID with the arrow key, press <Enter> and select a RAID level from the list that displays.
   
   
6. Select Reconstruct and press <Enter> to reconstruct the logical drive.
   
   

You are prompted to start the reconstruction. A progress bar for the reconstruction displays.

Drive Roaming

Drive roaming occurs when the hard drives are changed to different target IDs or channels on the same controller. When the drives are placed on different channels, the controller detects the RAID configuration from the configuration data on the drives.

NOTE: In a clustering environment, drive roaming is supported within the same channel only.

Configuration data is saved in both non-volatile random access memory (NVRAM) on the RAID controller and on the hard drives attached to the controller. This maintains the integrity of the data on each drive, even if the drives have changed their target ID.

NOTE: If you move a drive that is currently being rebuilt, the rebuild operation will restart, not resume.

Perform the following steps to use drive roaming:

1. Turn off all power to the server and all hard drives, enclosures, and system components, then disconnect power cords from the system.
   
   
2. Open the host system by following the instructions in the host system technical documentation.
   
   
3. Move the drives to different positions on the backplane to change the SCSI ID.
   
   
4. Determine the SCSI ID and SCSI termination requirements.
   
   

NOTE: The default for SCSI termination is onboard SCSI termination enabled.

5. Perform a safety check.
   
   
   • Make sure the drives are inserted properly.
     
     
   • Close the cabinet of the host system.
     
     
   • Turn power on after completing the safety check.
     
     
6. Power on the system.
   
   

The controller then detects the RAID configuration from the configuration data on the drives.

Drive Migration

Drive migration is the transfer of a set of hard drives in an existing configuration from one controller to another. The drives must remain on the same channel and be reinstalled in the same order as in the original configuration. The controller to which you migrate the drives cannot have an existing configuration.

NOTE: Only complete configurations can be migrated; individual virtual disks cannot be migrated.

NOTE: Drive roaming and drive migration cannot be supported at the same time.

Perform the following steps to migrate drives:

1. Make sure that you clear the configuration on the system to which you migrate the drives, to prevent a configuration data mismatch between the hard drives and the NVRAM.
   
   

NOTE: When you perform a drive migration, move only the disks that make up the logical drive (not all the physical disks in an array), so you will not see an NVRAM mismatch error (providing a configuration is on the destination controller). The NVRAM mismatch error appears only if you move all of the physical drives to the other controller.

2. Turn off all power to the server and all hard drives, enclosures, and system components, then disconnect power cords from the systems.
   
   
3. Open the host systems by following the instructions in the host system technical documentation.
   
   
4. Remove the unshielded, twisted pair, SCSI ribbon cable connectors from the internal drives or the shielded cables from the external drives you want to migrate.
   
   
   • Make sure pin 1 on the cable matches pin 1 on the connector.
     
     
   • Make sure that the SCSI cables conform to all SCSI specifications.
     
     
5. Remove the hard drives from the first system and insert them into drive bays on the second.
   
   
6. Connect the SCSI cables to the hard drives in the second system.
   
   
7. Determine the SCSI ID and SCSI termination requirements.
   
   

NOTE: The default for SCSI termination is onboard SCSI termination enabled.

8. Perform a safety check.
   
   
   • Make sure all cables are properly attached.
     
     
   • Make sure the RAID controller is properly installed.
     
     
   • Close the cabinet of the host system.
     
     
   • Turn power on after completing the safety check.
     
     
9. Power on the system.
   
   

The controller then detects the RAID configuration from the configuration data on the drives.

Deleting Logical Drives

This RAID controller supports the ability to delete any unwanted logical drives and use that space for a new logical drive. You can have an array with multiple logical drives and delete a logical drive without deleting the whole array.

After you delete a logical drive, you can create a new one. You can use the configuration utilities to create the next logical drive from a free space (`hole'), and from the newly created arrays. The configuration utility provides a list of configurable arrays where there is a space to configure. In the BIOS Configuration Utility, you must create a logical drive in the hole before you create a logical drive using the rest of the disk.

NOTE: Warning messages display about the effect of deleting an array. You must accept two warning statements before the array deletion is completed.

NOTICE: The deletion of the logical drive can fail under certain conditions: During a rebuild, initialization or check consistency of a logical drive.

To delete logical drives, perform the following steps in the BIOS Configuration Utility:

1. Select Objects—> Logical Drive from the Management Menu.
   
   

The logical drives display.

2. Use the arrow key to highlight the logical drive you want to delete.
   
   
3. Press <Del> to delete the logical drive.
   
   

This deletes the logical drive and makes the space it occupied available for you to make another logical drive.

Patrol Read

The Patrol Read function is designed as a preventive measure to detect hard drive errors before drive failure can threaten data integrity. Patrol Read can find and possibly resolve any potential problem with physical drives prior to host access. This can enhance overall system performance because error recovery during a normal I/O operation may not be necessary.

Patrol Read Behavior

The following is an overview of Patrol Read behavior:

1. Patrol Read runs on all disks on the adapter that are configured as part of an array including hot spares. Patrol Read will not run on unconfigured drives, which are drives that are not part of an array or that are in a ready state.
   
   
2. Patrol Read adjusts the amount of RAID controller resources dedicated to Patrol Read operations based on outstanding disk I/O. For example, if the server is busy processing I/O operation, then Patrol Read will use less resources to allow the I/O to take a higher priority.
   
   
3. Patrol Read operates on all configured physical drives on the controller and there is no method to deselect drives from the Patrol Read operations.
   
   
4. If the server reboots during a Patrol Read iteration, Patrol Read will restart from zero percent if in Auto Mode. In Manual Mode, Patrol Read does not restart upon a reboot. Manual Mode assumes you have selected a window of time dedicated to running Patrol Read and the server will be available during that time.
   
   

Configuration

You can use the BIOS Configuration Utility to configure Patrol Read. Dell OpenManage Array Manager and OpenManage System Storage Management cannot configure Patrol Read. Patrol Read can be started and stopped using MegaPR from within Window and Linux.

Blocked Operations

If any of the following conditions exist, then Patrol Read will not run on any of the affected disks:

• An unconfigured disk (the disk is in the READY state)
  
  
• Disks that are members of a logical drive undergoing a reconstruction
  
  
• Disks that are members of a logical drive that is currently owned by the peer adapter in a cluster configuration
  
  
• Disks that are members of a logical drive undergoing a Background Initialization or Check Consistency
  
  

Patrol Read Scheduling Details

The following describes the scheduling details for Patrol Read:

1. The PERC controller default settings sets Patrol Read to Auto mode. The Patrol Read mode can be set to Auto or Manual mode in the BIOS Configuration Utility.
   
   
2. In Auto mode, Patrol Read runs continuously on the system and is scheduled to start a new Patrol Read within four hours after the last iteration is completed.
   
   
3. When Patrol Read Mode is changed from Auto to Manual, Manual Halt, or Disabled, the Next execution will start at: field will be set to N/A.
   
   

Configuring Patrol Read

Patrol Read can be set to Manual or Automatic mode. When in Manual mode, the BIOS Configuration Utility can start and stop a Patrol Read iteration. MegaPR can be used to start and stop a Patrol Read iteration from Linux or Windows.

The BIOS Configuration Utility has options to configure Patrol Read on the controller. Access the Objects→ Adapter→ Patrol Read Options menu. Press <Enter> to open the Patrol Read submenu, which displays the following items:

• Patrol Read Mode
  
  
• Patrol Read Status
  
  
• Patrol Read Control
  
  

Patrol Read Mode

The current setting displays as Manual/Auto/Disabled. When you select this option, a window opens to display the following options, with the current setting highlighted:

1. Manual
   
   
2. Auto
   
   
3. Manual Halt
   
   
4. Disabled
   
   

You can change the setting by selecting a different value upon confirmation.

Patrol Read Status

When you select Patrol Read Status and press <Enter>, a window opens to display these options:

1. Number of Iterations Completed =
   
   
2. State = Active/Stopped
   
   
3. Next Execution will Start at
   
   

The current state is shown at the second option that allows you to display the percentage of completion by pressing <Enter> key if the Patrol Read state is Active. The first and the third options are read only.

Patrol Read Control

When you select this option, a window opens to display the following options:

1. Start
   
   
2. Stop
   
   

NOTE: Start or Stop options are available in manual mode only.

Behavior Details

The following are behavior details for Patrol Read:

1. Setting Patrol Read in Manual mode does not start Patrol Read. It only sets the mode so that you can select Start whenever you want to run Patrol Read. Once the mode is MANUAL, it stays in that mode until you change it.
   
   
2. Setting the mode to AUTOMATIC starts Patrol Read; when the Patrol Read operation is complete, it will set itself to run within four hours of the last iteration completion.
   
   

MegaPR Utility

MegaPR is a utility for managing and reporting the status of Patrol Read from the operating system. There are two versions of the utility: one for Windows 2000/2003, and one for Linux (RHEL 2.1, 3, and 4).

Available options are (help for individual options is available by typing cmd –[option] ?):

• –dispPR: Display Patrol Read status.
  
  
• –startPR: Start Patrol Read.
  
  
• –stopPR: Stop Patrol Read.
  
  

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