In order to implement RAID functions, RAID controllers must create a virtual disk. A virtual disk refers to storage created by a RAID controller from one or more physical disks. Although a virtual disk may be created from several physical disks, it is seen by the operating system as a single disk. Depending on the RAID level used, the virtual disk may retain redundant data in case of a disk failure or have particular performance attributes. See "Understanding RAID Concepts" for more information.
NOTE: Virtual disks can only be created on a RAID controller.
Considerations Before Creating Virtual Disks
Different controllers have particular characteristics in the way they implement virtual disks. These characteristics may include use of disk space, limitations on the number of virtual disks per controller, and so on. It can be helpful to understand these characteristics before creating virtual disks on the controller.
The following sections describe controller information that applies to virtual disks:
NOTE: In addition to this document, review the hardware documentation that is
provided with the controllers. Reviewing the hardware documentation along with
this document may provide a better understanding of the controller limitations.
Virtual Disk Considerations for PERC 5/E, PERC 5/i, PERC 6/E, and PERC
6/I Controllers
In addition to the considerations described in this section, you should also be aware of the controller limitations described in "Number of Physical Disks per Virtual Disk."
Be aware that the following considerations apply when creating virtual disks:
Creating virtual disks on PERC 5/E, PERC 5/i, PERC 6/E, and PERC 6/I controllers. When you create a virtual disk, you specify which physical disks are to be included in the virtual disk. The virtual disk you create spans the specified physical disks. Depending on the size of the virtual disk, the virtual disk may not consume all of the space on the physical disks. Any leftover space on the physical disks cannot be used for a second virtual disk unless the physical disks are of equal size. In addition, when the physical disks are of equal size and you can use the leftover space for a second virtual disk, this new virtual disk cannot expand to include any physical disks not included in the original virtual disk.
Expanding virtual disks. You can only use the Reconfigure task to expand a virtual disk that uses the full capacity of its member physical disks. For more information, see "Virtual Disk Task: Reconfigure (Step 1 of 3)."
Reconfiguring virtual disks. The Reconfigure task is not available when you have more than one virtual disk using the same set of physical disks. You can, however, reconfigure a virtual disk that is the only virtual disk residing on a set of physical disks. See "Virtual Disk Task: Reconfigure (Step 1 of 3)" for more information.
Virtual disk names not stored on controller. The names of the virtual disks that you create are not stored on the controller. This means that if you reboot using a different operating system, the new operating system may rename the virtual disk using its own naming conventions.
Creating and deleting virtual disks on cluster-enabled controllers. There are particular considerations for creating or deleting a virtual disk from a cluster-enabled controller.
Implementing channel redundancy. A virtual disk is channel-redundant when it maintains redundant data on more than one channel. If one of the channels fails, data will not be lost because redundant data resides on another channel. For more information, see "Channel Redundancy and Thermal Shutdown."
Rebuilding data. An failed physical disk that is used by both redundant and nonredundant virtual disks cannot be rebuilt. Rebuilding a failed physical disk in this situation requires deleting the nonredundant virtual disk.
Virtual Disk Considerations on Linux
On some versions of the Linux operating system, the virtual disk size is limited to 1TB. Before creating a virtual disk that is larger than 1TB, you should make sure that your operating system supports this virtual disk size. The support provided by your operating system depends on the version of the operating system and any updates or modifications that you have implemented. In addition, you should investigate the capacity of your peripheral devices to support a virtual disk that is larger than 1TB. See your operating system and device documentation for more information.
Number of Physical Disks per Virtual Disk
There are limitations on the number of physical disks that can be included in the virtual disk. These limitations depend on the controller. When creating a virtual disk, controllers support a certain number of stripes and spans (methods for combining the storage on physical disks). Because the number of total stripes and spans is limited, the number of physical disks that can be used is also limited. The limitations on stripes and spans affect the possibilities for RAID levels as follows:
Maximum number of spans affects RAID 10, RAID 50, and RAID 60.
Maximum number of stripes affects RAID 0, RAID 5, RAID 50, RAID 6, and RAID 60.
Number of physical disks in a mirror is always 2. This affects RAID 1 and RAID 10.
In the case of RAID 50 and RAID 60, you can use a greater number of physical disks than is possible for the other RAID levels. RAID 10 on a SAS controller with firmware version 6.1 can use a maximum of 256 physical disks. However, the number of connectors on the controller imposes limitations on how many physical disks can be included in a virtual disk when using RAID 10, RAID 50, or RAID 60. This is because only a limited number of physical disks can be physically attached to the controller.
For information on how many physical disks a controller supports per virtual disk, see the virtual disk specifications for the controller in "Supported Features."
Maximum Number of Virtual Disks per Controller
Controllers have limitations on how many virtual disks can be created on the controller. For information on how many virtual disks the controller supports, see the virtual disk specifications for the controller in "Supported Features."
Calculation for Maximum Virtual Disk Size and the Create Virtual Disk
Express Wizard
The Create Virtual Disk Express Wizard displays the minimum and maximum values for the virtual disk size. This section describes how the maximum possible size for the virtual disk is calculated based on the controller type. To identify the controller type, see "RAID Controller Technology: SAS."
SAS RAID Controllers
When using a SAS controller, the controller calculates the maximum virtual disk size based on the available disk space provided by the minimum number of physical disks required to create the RAID level you selected. For example, if you specified a RAID 5, then the controller calculates the maximum virtual disk size based on three physical disks, because only three physical disks are required to create a RAID 5.
Channel Redundant Virtual Disks
When creating a virtual disk, it is possible to use disks attached to different channels to implement channel redundancy. This configuration might be used for disks that reside in enclosures subject to thermal shutdown. See the following for more information:
In order to implement RAID functions, you need to create a virtual disk. A virtual disk refers to storage created by a RAID controller from one or more physical disks. Although a virtual disk may be created from several physical disks, it is seen by the operating system as a single disk. See "What Is RAID?" for more information.
Storage Management provides wizards to help you create a virtual disk:
The Create Virtual Disk Express Wizard calculates an appropriate virtual disk layout based on the available space and controller considerations. Using the Express Wizard, you can quickly create a virtual disk using recommended selections. See "Create Virtual Disk Express Wizard (Step 1 of 2)" for more information.
The Create Virtual Disk Advanced Wizard allows you to specify the read, write, and cache policy for the virtual disk. You can also select the physical disks and the controller connector to be used. You need a good knowledge of RAID levels and hardware to use the Advanced Wizard. See "Create Virtual Disk Advanced Wizard (Step 1 of 4)" for more information.
You may also want to refer to the following related sections:
Starting and Target RAID Levels for Virtual Disk Reconfiguration
After you have created a virtual disk, the possibilities for reconfiguring the virtual disk depend on the controller, RAID level, and available physical disks. The following table describes the possible scenarios for reconfiguring a virtual disk. For more information on the RAID levels, see "Choosing RAID Levels."
Table 13-1. Virtual Disk Reconfiguration
Controller
Starting RAID Level
Target RAID Level
Comments
PERC 6/E, PERC 6/I, CERC 6/I
RAID 0
RAID 1
Add a single disk
RAID 0
RAID 0, RAID 5
Add at least one additional disk.
RAID 0
RAID 6
RAID 6 requires a minimum of 4 disks.
Reconfiguration from RAID 0 to RAID 6 requires at least 2 additional disks even when this exceeds the 4-disk minimum required by RAID 6.
The virtual disk Check Consistency task verifies the accuracy of the redundant (parity) information. This task only applies to redundant virtual disks. When necessary, the Check Consistency task rebuilds the redundant data.
To verify a virtual disk's redundant information:
Locate the controller on which the virtual disk resides in the tree view.
Expand the controller object until the Virtual Disks object is displayed.
Select the Check Consistency task from the virtual disk's drop-down
menu and click Execute.
If you have a redundant virtual disk, you can reconstruct the contents of a failed physical disk onto a new disk or a hot spare. A rebuild can take place during normal operation, but it will degrade performance. The following sections provide additional information on rebuilding disks.
"Replacing a Failed Disk" describes how to replace a failed physical disk and initiate a rebuild.
"Set Rebuild Rate" describes how to set the rebuild rate on selected controllers.
This property displays the current status of the virtual disk. Possible values are:
Ready — The virtual disk is functioning normally.
Degraded — A physical disk in a redundant virtual disk is not online.
Resynching — A consistency check is being performed on the virtual disk.
Resynching Paused — A consistency check has been paused on the virtual disk.
Regenerating — A physical disk in the virtual disk is rebuilding.
Reconstructing — The virtual disk configuration has changed. The physical disks included in the virtual disk are being modified to support the new configuration.
Failed — The virtual disk has encountered a failure of one or more components and is no longer functioning.
Failed Redundancy — This state is displayed when the initial consistency check for the virtual disk is cancelled or is not successful. This state may also be displayed when a RAID 1, RAID 10 or RAID 1-concatenated virtual disk suffers a physical disk failure. In addition, there are other conditions related to disk failures and the firmware that can cause a virtual disk to display a Failed Redundancy state.
Background Initialization — A background initialization is being performed on the virtual disk.
On some controllers, the virtual disk state is not updated until the controller performs an I/O operation.
Degraded Redundancy — This state is applicable to RAID 6 only in which a physical disk in a redundant virtual disk is not online, but the virtual disk is still accessible and functioning.
Layout
This property displays the RAID level.
Size
This property displays the total capacity of the virtual disk.
The algorithm for calculating the virtual disk size rounds a value of 0.005 or less down to 0.00 and a value between 0.006 and 0.009 up to 0.01. For example, a virtual disk size of 819.725 will be rounded down to 819.72. A virtual disk size of 819.726 will be rounded up to 819.73.
Device Name
This property displays the operating system device name for this object.
Bus Protocol
This property displays the technology that the physical disks included in the virtual disk are using. Possible values are:
SAS — Serial Attached SCSI
SATA — Serial Advanced Technology Attachment (SATA)
Media
This property displays the media type of the physical disks present in the virtual disk. The possible values are:
HDD—Hard Disk Drive. A HDD is a non-volatile storage device which stores digitally-encoded data on rapidly rotating platters with magnetic surfaces.
SSD—Solid State Drive. An SSD is a data storage device that uses solid-state memory to store persistent data.
Unknown—Storage Management is unable to determine the media type of the physical disk.
NOTE: You cannot have a mix of HDD and SSD media on a virtual
disk. Also, you cannot have a mix of SAS and SATA drives on the
virtual disk.
Do the following to execute a virtual disk drop-down menu task:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select a task from the Available Tasks drop-down menu.
Click Execute.
NOTE: Different controllers support different features. For this reason, the tasks
displayed on the Tasks drop-down menu can vary depending on which controller is
selected in the tree view. If no tasks can be performed because of controller or
system configuration limitations, then the Tasks drop-down menu displays No Task
Available.
Use the Reconfigure task to change the virtual disks properties. For example, you can use this task to add physical disks or change the RAID level. See "Virtual Disk Task: Reconfigure (Step 1 of 3)" for more information.
Use the Format, Initialize, Slow Initialize, or Fast Initialize task to erase the files and remove the file systems on a virtual disk. Some controllers require that you initialize a virtual disk before it can be used. See "Format and Initialize; Slow and Fast Initialize" for more information.
Use the Cancel Format or Cancel Initialize task to cancel the virtual disk format or initialize while it is in progress. For more information on virtual disk format or initialize, see "Format and Initialize; Slow and Fast Initialize."
Because the initialization is run in the background, other processes can continue while the initialization completes.
The background initialization of a redundant virtual disk prepares the virtual disk for parity information and improves write performance. It is important that the background initialization be allowed to run to completion. You can, however, cancel the background initialization. When you do so, the controller will restart the background initialization at a later time.
Use the Cancel Background Initialization task to cancel a background initialization on a virtual disk.
Use the Restore Dead Segments task to recover data from a RAID-5 virtual disk that has been corrupted. The Restore Dead Segments task attempts to reconstruct data from a corrupt portion of a physical disk included in a RAID-5 virtual disk. The Restore Dead Segments task uses the parity or redundant information to reconstruct the lost data. This task is not always able to recover lost data.
Use the Assign Dedicated Hot Spare task to assign a disk as a backup for a single virtual disk. See "Assign and Unassign Dedicated Hot Spare" for more information.
Use the Check Consistency task to verify the accuracy of the redundant (parity) information. This task only applies to redundant virtual disks. When necessary, the Check Consistency task rebuilds the redundant data. If the virtual disk is in a Failed Redundancy state, running a check consistency may return the virtual disk to a Ready state.
Use the Pause Check Consistency task to pause a check consistency while it is in progress.
NOTE: The Pause Check Consistency task updates the virtual disk state property to
Resynching Paused immediately. The progress property may continue to increment
for up to three seconds. This time delay occurs because the polling task may take
up to three seconds to query the task information and update the display.
The Blink and Unblink tasks blink or unblink the lights on the physical disks included in the virtual disk. See "Blink and Unblink (Virtual Disk)" for more information.
Use the Change Policy task to change a virtual disk's read, write, or cache policy. Changes to the read, write, and cache policy only apply to the virtual disk that you have selected. This task does not change the policy for all virtual disks on the controller. See "RAID Controller Read, Write, Cache, and Disk Cache Policy" for more information.
You can also modify the physical disk cache policy using this command.
Use the Replace Member Disk task to copy data from a physical disk, which is a member of a virtual disk, to another physical disk by providing the Replace Member Configuration option. You can initiate multiple copies of data from different array groups. See "Virtual Disk Task: Replace Member Disk (Step 1 of 2)" for more information.
The Create Virtual Disk Express Wizard calculates an appropriate virtual disk configuration based on the available space and controller considerations. When using the Express Wizard, you select the RAID level and size for the virtual disk. The wizard selects a recommended disk configuration for you that matches your RAID and size selection.
If you want to make your own selections for the virtual disk configuration, click Go To Advanced Wizard.
To Create a Virtual Disk Express Wizard: Step 1 of 2
Click the radio button to select the correct RAID level.
Select RAID 0 for striping. This selection groups n disks together as one large virtual disk with a total capacity of n disks. Data is stored to the disks alternately so that they are evenly distributed. Data redundancy is not available in this mode. Read and write performance is enhanced.
Select RAID 1 for mirroring disks. This selection groups two disks together as one virtual disk with a capacity of one single disk. The data is replicated on both disks. When a disk fails, the virtual disk continues to function. This feature provides data redundancy and good read performance, but slightly slower write performance. Your system must have at least two disks to use RAID 1.
Select RAID 5 for striping with distributed parity. This selection groups n disks together as one large virtual disk with a total capacity of (n-1) disks. When a disk fails, the virtual disk continues to function. This feature provides better data redundancy and read performance, but slower write performance. Your system must have at least three disks to use RAID 5.
Select RAID 6 for striping with additional distributed parity. This selection groups n disks as one large virtual disk with a capacity of (n-2) disks. The virtual disk remains functional with up to two disk failures. RAID 6 provides better read performance, but slower write performance. Your system must have at least four disks to use RAID 6.
Select RAID 10 for striping over mirror sets. This selection groups n disks together as one large virtual disk with a total capacity of (n/2) disks. Data is striped across the replicated mirrored pair disks. When a disk fails, the virtual disk continues to function. The data is read from the surviving mirrored pair disk. This feature provides the best failure protection, read and write performance. Your system must have at least four disks to use RAID 10.
Select RAID 50 to implement striping across more than one span of physical disks. RAID 50 groups n*s disks as one large virtual disk with a capacity of s*(n-1) disks, where s is the number of spans and n is the number of disks within each span.
Select RAID 60 to implement striping across more than one RAID 6 span. RAID 60 Groups n*s disks as one large virtual disk with a capacity of s*(n-2) disks, where s is the number of spans and n is the number of disks within each span. RAID 60 provides increased data protection and better read performance, but slower write performance.
Type a name for the virtual disk in the Name text box.
The virtual disk name can contain only alphanumeric characters as well as spaces, dashes and underscores. The maximum name length depends on the controller. In most cases, the maximum length is 15 characters. The name cannot start with a space or end with a space.
It is recommended that you specify a unique name for each virtual disk. If you have virtual disks with the same name, it will be hard to differentiate the alerts generated for these virtual disks.
In some cases, the virtual will be slightly larger than the size you specify. The Create Virtual Disk wizard may round up the size of the virtual disk to avoid rendering a portion of the physical disk space unusable.
Click Continue to go to the next screen or Exit Wizard if you want to
cancel.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
This screen displays the virtual disk attributes and enables you to assign a dedicated hot spare to the virtual disk.
Do the following:
Review the virtual disk attributes displayed in the Summary of Virtual
Disk Attributes and the Selected Physical Disks sections of the screen.
These sections display the selections you made using "Create Virtual Disk
Express Wizard (Step 1 of 2)" and the physical disks that the Express
Wizard selected.
Review the Assign Dedicated Hot Spare section. A hot spare is an
unused backup physical disk that can be used to rebuild data from a
redundant virtual disk. See "Protecting Your Virtual Disk with a Hot
Spare" for more information.
Select the Physical Disk check box if you want to assign a dedicated hot spare.
The Physical Disk check box is not available if the controller does not have a physical disk that is a suitable hot spare for the virtual disk you are creating. For example, the available physical disks may be too small to protect the virtual disk. If the Physical Disk check box is not available, you may need to specify a smaller virtual disk, use a different RAID level, or change the disk selection using the Create Virtual Disk Advanced wizard.
Do one of the following:
Click Finish to create the virtual disk with the attributes shown on this screen.
The Create Virtual Disk Advanced Wizard allows you to specify the read, write, and cache policy for the virtual disk. You can also select the physical disks and the controller connector to be used. You need a good knowledge of RAID levels and hardware to use the Advanced Wizard.
If you want to have the wizard choose a recommended virtual disk configuration for you, click Go To Express Wizard.
To Create a Virtual Disk Advanced Wizard: Step 1 of 4
Click the radio button to select the correct RAID level.
Select RAID 0 for striping. This selection groups n disks together as one large virtual disk with a total capacity of n disks. Data is stored to the disks alternately so that they are evenly distributed. Data redundancy is not available in this mode. Read and write performance is enhanced.
Select RAID 1 for mirroring disks. This selection groups two disks together as one virtual disk with a capacity of one single disk. The data is replicated on both disks. When a disk fails, the virtual disk continues to function. This feature provides data redundancy and good read performance, but slightly slower write performance. Your system must have at least two disks to use RAID 1.
Select RAID 5 for striping with distributed parity. This selection groups n disks together as one large virtual disk with a total capacity of (n-1) disks. When a disk fails, the virtual disk continues to function. This feature provides better data redundancy and read performance, but slower write performance. Your system must have at least three disks to use RAID 5.
Select RAID 6 for striping with additional distributed parity. This selection groups n disks as one large virtual disk with a capacity of (n-2) disks. The virtual disk remains functional with up to two disk failures. RAID 6 provides better read performance, but slower write performance. Your system must have at least four disks to use RAID 6.
Select RAID 10 for striping over mirror sets. This selection groups n disks together as one large virtual disk with a total capacity of (n/2) disks. Data is striped across the replicated mirrored pair disks. When a disk fails, the virtual disk continues to function. The data is read from the surviving mirrored pair disk. This feature provides the best failure protection, read and write performance. Your system must have at least four disks to use RAID 10.
Select RAID 50 to implement striping across more than one span of physical disks. RAID 50 groups n*s disks as one large virtual disk with a capacity of s*(n-1) disks, where s is the number of spans and n is the number of disks within each span.
Select RAID 60 to implement striping across more than one RAID 6 span. RAID 60 Groups n*s disks as one large virtual disk with a capacity of s*(n-2) disks, where s is the number of spans and n is the number of disks within each span. RAID 60 provides increased data protection and better read performance, but slower write performance.
Click Continue to go to the next screen or Exit Wizard if you want to
cancel.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
This screen enables you to select which disks will be used to create the virtual disk. The items displayed on this screen depend on the selections you made in "Create Virtual Disk Advanced Wizard (Step 1 of 4)."
NOTE: For a controller that has more than one channel, it may be possible to
configure a virtual disk that is channel-redundant. See "Channel Redundancy and
Thermal Shutdown" for more information.
Depending on the RAID level you selected and the virtual disk size, this screen displays the disks and connectors (channels or ports) available for configuring the virtual disk.
The following is an example of what might be displayed:
Connector 0
The Connector section of the screen displays the controller's connectors and the disks attached to each connector. Select the disks to be included in the virtual disk. In this example, the controller has a single connector with five disks.
Physical disk 0:0
Physical disk 0:1
Physical disk 0:2
Physical disk 0:3
Physical disk 0:4
Physical Disks Selected
The Physical Disks Selected section of the screen displays the disks you have chosen. In this example, two disks are selected.
Physical disk 0:0
Physical disk 0:1
Each RAID level has specific requirements for the number of disks that must be selected. RAID 10, RAID 50, and RAID 60 also have requirements for how many disks must be included in each stripe or span.
If the controller is a SAS controller with firmware versions 6.1 and later and you selected RAID 10, the user interface displays the following:
Select All check box— Enables you to select all the physical disks in all the enclosures.
Enclosure check box — Enables you to select all physical disks in the enclosure.
NOTE: The Select All and Enclosure check boxes enable you to edit spans
after selecting the physical disks that comprise them. You can remove a span
and re-specify a span with different physical disks before proceeding.
Number of disks per span drop down — Enables you to select the number of disks in each span (default =2). This option is available only on SAS controllers with firmware version 6.1 and later.
NOTE: On a SAS controller with firmware version 6.1 and later, RAID 10
supports only even number of disks per span and a maximum of 8 spans with
32 disks.
Let us consider that the controller has three enclosures with six physical disks each (total number of available disks = 3 x 6 =18 disks). If you select four disks per span, the controller will create four spans (18 disks/4 disks per span = 4 spans). The last two disks of the last enclosure will not be part of RAID 10.
Intelligent Mirroring — Automatically calculates the span composition based on the physical disks you select
NOTE: Selecting this option disables the Number of disks per span option.
Storage Management uses the following intelligence to calculate the optimum span composition:
Determining span calculation:
Calculating the number of disks that can be utilized out of selected disks.
Maximizing the number of spans in order to increase the I/O performance
Determining the mirror for the physical disks:
The mirror is determined in a way that ensures maximum redundancy. The algorithm will also try to match a physical disk for its mirror to a disk that is closest to it in size. However, Intelligent Mirroring places more importance on redundancy over size.
The algorithm determines the candidate mirror in the following order:
Across connectors at the same level of enclosure and of same size
Across connectors in the enclosure that are not at the same level but of same size
Across enclosures connected to same connector and to a disk of same size
Across connectors at the same level of enclosure and of acceptable size difference
Across connectors in the enclosure that are not at the same level of the enclosure but with a physical disk of acceptable size difference
Within the enclosure with a physical disk of acceptable size difference
If the physical disk cannot be mirrored because the size difference is not acceptable, the disk will not be mirrored and hence dropped from the span, and number of span and disk in the span will be recalculated.
Click Continue when you have completed the disk selection. If you want to cancel the virtual disk, click Exit Wizard. If you want to return to the previous screen and change your selections, click Go Back To Previous Page.
This screen enables you to select attributes for the virtual disk. These attributes include the name, size and read, write, and cache policy. Depending on the controller and your previous virtual disk selections, the items displayed on this screen can vary.
Do the following:
Type the name of the virtual disk in the Name text box.
The virtual disk name can contain only alphanumeric characters as well as spaces, dashes and underscores. The maximum name length depends on the controller. In most cases, the maximum length is 15 characters. The name cannot start with a space or end with a space.
It is recommended that you specify a unique name for each virtual disk. If you have virtual disks with the same name, it will be hard to differentiate the alerts generated for these virtual disks.
The Size text box displays the default size of the virtual disk, depending
upon the RAID configuration you selected. You can specify a different size.
The virtual disk size must be within the minimum and maximum values
displayed near the Size text box. In some cases, the virtual will be slightly
larger than the size you specify. The Create Virtual Disk wizard may round
up the size of the virtual disk to avoid rendering a portion of the physical
disk space unusable.
Select a stripe size from the Stripe Size drop-down menu. The stripe size
refers to the amount of space that each stripe consumes on a single disk.
See "What Is RAID?" for more information.
NOTE: There is limited support for write policy on controllers that do not have a
battery. See "Write Policy" for more information. The cache policy is not supported
on any controller that does not have a battery. See "RAID Controller Read, Write,
Cache, and Disk Cache Policy" for more information.
Click Continue to go to the next screen If you want to cancel the virtual
disk, click Exit Wizard. If you want to return to the previous screen and
change your selections, click Go Back To Previous Page.
This screen displays the virtual disk attributes and enables you to assign a dedicated hot spare to the virtual disk.
Do the following:
Review the virtual disk attributes displayed in the Summary of Virtual
Disk Attributes and the Selected Physical Disks sections of the screen.
These sections display the selections you made using "Create Virtual Disk
Express Wizard (Step 1 of 2)" and the physical disks that the Express
Wizard selected.
Review the Assign Dedicated Hot Spare section. A hot spare is an
unused backup physical disk that can be used to rebuild data from a
redundant virtual disk. See "Protecting Your Virtual Disk with a Hot
Spare" for more information.
The Create Virtual Disk Advanced wizard displays a check box next to each physical disk that is suitable as a dedicated hot spare. Select a Physical Disk check box if you want to assign a dedicated hot spare.
The Physical Disk check box is not available if the controller does not have a physical disk that is a suitable hot spare for the virtual disk you are creating. For example, the available physical disks may be too small to protect the virtual disk. If the Physical Disk check box is not available, you may need to specify a smaller virtual disk, use a different RAID level, or change the disk selection.
In the edit mode, you cannot alter the number of physical disks per span. If there are enough available physical disks, you can reduce or increase the number of spans. You can also alter the contents of a span by removing that span and selecting a new physical disk to comprise that span.
To successfully create a virtual disk, a minimum of two spans must exist at all times.
The Reconfigure task enables you to change the virtual disk configuration. Using this task, you can change the RAID level and increase the virtual disk size by adding physical disks. On some controllers, you can also remove physical disks.
NOTE: You cannot reconfigure a virtual disk on a controller that is operating in
cluster mode.
NOTE: On the PERC 5/E and PERC 6/E controllers, you can create no more than 64
virtual disks. After you have reached this limit, you will no longer be able to
reconfigure any of the virtual disks on the controller.
NOTE: On Linux, if you do a reconfigure on the same controller on which the
operating system resides, you may experience extremely slow system performance
until the reconfigure is complete.
Select the physical disks that you want to include in the virtual disk. You
can expand the virtual disk's capacity by adding additional physical disks.
On some controllers, you can also remove physical disks.
The changes you make to the physical disk selection are displayed in the Selected Physical Disks table.
NOTE: For a controller that has more than one channel, it may be possible to
configure a virtual disk that is channel-redundant. See "Channel Redundancy and
Thermal Shutdown" for more information.
Click Continue to go to the next screen or Exit Wizard if you want to
cancel.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select Reconfigure from the Available Tasks drop-down menu.
This screen enables you to select the RAID level and size for the reconfigured virtual disk.
To Reconfigure a Virtual Disk: Step 2 of 3
Select the new RAID level for the virtual disk. The available RAID levels
depend on the number or physical disks selected and the controller. The
following describes possible RAID levels:
Select RAID 0 for striping. This selection groups n disks together as one large virtual disk with a total capacity of n disks. Data is stored to the disks alternately so that they are evenly distributed. Data redundancy is not available in this mode. Read and write performance is enhanced.
Select RAID 1 for mirroring disks. This selection groups two disks together as one virtual disk with a capacity of one single disk. The data is replicated on both disks. When a disk fails, the virtual disk continues to function. This feature provides data redundancy and good read performance, but slightly slower write performance. Your system must have at least two disks to use RAID 1.
Select RAID 5 for striping with distributed parity. This selection groups n disks together as one large virtual disk with a total capacity of (n-1) disks. When a disk fails, the virtual disk continues to function. This feature provides better data redundancy and read performance, but slower write performance. Your system must have at least three disks to use RAID 5.
Select RAID 6 for striping with additional parity information. This selection groups n disks as one large virtual disk with a capacity of (n-2) disks. Two sets of parity information is alternately stored on all disks. The virtual disk remains functional with up to two disk failures.
Select RAID 10 for striping over mirror sets. This selection groups n disks together as one large virtual disk with a total capacity of (n/2) disks. Data is striped across the replicated mirrored pair disks. When a disk fails, the virtual disk continues to function. The data is read from the surviving mirrored pair disk. This feature provides the best failure protection, read and write performance. Your system must have at least four disks to use RAID 10.
Type the size for the reconfigured virtual disk in the Size text box. The
minimum and maximum allowable size is displayed under the Size text
box. These values reflect the new capacity of the virtual disk after any
addition or deletion of physical disks which you may have chosen in
"Virtual Disk Task: Reconfigure (Step 1 of 3)."
Click Continue to go to the next screen or Exit Wizard if you want to
cancel.
This screen enables you to review your changes before completing the virtual disk reconfiguration.
To Reconfigure a Virtual Disk: Step 3 of 3
Review your changes. The New Virtual Disk Configuration table displays
the changes you have made to the virtual disk. The Previous Virtual Disk
Configuration displays the original virtual disk prior to reconfiguration.
Click Finish to complete the virtual disk reconfiguration. If you want to
exit without changing the original virtual disk, click Exit Wizard.
NOTE: On some controllers, performing a Rescan while a reconfiguration is in
progress will cause the virtual disk configuration and the physical disk state to
display incorrectly. For example, changes to the virtual disk's RAID level may not be
displayed and the state of physical disks that were added to the virtual disk may
display as Ready instead of Online.
The Format or Initialize task erases the files and removes the file systems on virtual disks while keeping the virtual disk configuration intact. Formatting or initializing a virtual disk destroys all data on the virtual disk. If the boot partition resides on the virtual disk, it will be destroyed by the format operation.
Some controllers have BIOS settings for a fast initialize or a slow initialize. In this case, the Initialize task performs the type of initialization (fast or slow) that is specified in the BIOS.
NOTE: On a Linux system, you cannot format a virtual disk that contains a mounted
volume.
Considerations for Fast Initialize
Use the Fast Initialize task to initialize all physical disks included in the virtual disk. The Fast Initialize task updates the metadata on the physical disks so that all disk space is available for future write operations. The initialize can be completed quickly because existing information on the physical disks is not erased, although future write operations will overwrite any information that remains on the physical disks.
NOTE: Doing a Fast Initialize causes existing data to be inaccessible. This task
should be considered data destructive.
In comparison with the Slow Initialize task, the Fast Initialize task has the following advantages:
The Fast Initialize task takes less time to complete.
The Fast Initialize task does not write zeroes to the disk blocks on the physical disks. Because the Fast Initialize task does not perform a write operation, it causes less degradation to the disk than does the Slow Initialize task.
If you have had trouble with a physical disk or suspect that it has bad disk blocks, you may want to perform a Slow Initialize task, as this task remaps bad blocks and writes zeroes to all disk blocks.
Considerations for Slow Initialize
Use the Slow Initialize task to initialize all physical disks included in the virtual disk. The Slow Initialize task updates the metadata on the physical disks and erases all existing data and file systems.
In comparison with the Fast Initialize task, you may want to use the Slow Initialize task if you have had trouble with a physical disk or suspect that it has bad disk blocks. The Slow Initialize task remaps bad blocks and writes zeroes to all disk blocks.
The Slow Initialize task initializes one physical disk at a time. Each physical disk displays the Clear state while being initialized. During the time that the physical disk is in the Clear state, the Cancel Clear physical disk task is available. Performing a Cancel Clear task on the physical disk causes the Slow Initialize task to be cancelled for the entire virtual disk and all member physical disks. See "Clear Physical Disk and Cancel Clear" for more information.
Formatting or Initializing a Disk
To format or initialize a disk:
Review the virtual disk that will be destroyed by the Format or Initialize
and make sure that vital data will not be lost. Click Blink at the bottom of
the screen to blink the physical disks included in the virtual disk.
Depending on the task you are initiating, click the following button when
ready:
Format
Initialize
Slow Initialize
Fast Initialize
To exit without formatting or initializing the virtual disk, click Go Back To Virtual Disk Page.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Depending on the task you want to initiate, select one of the following
from the Available Tasks drop-down menu.
Deleting a virtual disk destroys all information including file systems and volumes residing on the virtual disk.
NOTE: When deleting virtual disks, all assigned global hot spares may be
automatically unassigned when the last virtual disk associated with the controller is
deleted.
To delete a virtual disk:
To identify which physical disks are included in the virtual disk, click Blink. The LED lights on the physical disks will blink for 30 to 60 seconds.
When deleting a virtual disk, the following considerations apply:
There are particular considerations for deleting a virtual disk from a cluster-enabled controller.
It is recommended that you reboot the system after deleting the virtual disk. Rebooting the system ensures that the operating system recognizes the disk configuration correctly.
If you delete a virtual disk and immediately create a new virtual disk with all the same characteristics as the one that was deleted, the controller will recognize the data as if the first virtual disk were never deleted. In this situation, if you don't want the old data after recreating a new virtual disk, reinitialize the virtual disk.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select Delete from the Available Tasks drop-down menu.
Renaming a virtual disk enables you to change the virtual disk's name. The numbering format for the virtual disk remains unchanged.
Depending on the controller you have, there are different considerations regarding the controller BIOS:
The virtual disk name can contain only alphanumeric characters as well as spaces, dashes and underscores. The maximum name length depends on the controller. In most cases, the maximum length is 15 characters. The name cannot start with a space, end with a space, or be left blank.
To rename a virtual disk:
Type the new name in the text box.
Click Rename. If you want to exit without renaming the virtual disk, click
Go Back To Virtual Disk Page.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select Rename from the Available Tasks drop-down menu.
Use the Split Mirror task to separate mirrored data originally configured as a RAID 1, RAID 1-concatenated, or RAID 10 virtual disk. Splitting a RAID 1 or RAID 1-concatenated mirror creates two concatenated nonredundant virtual disks. Splitting a RAID 10 mirror creates two RAID 0 (striped) nonredundant virtual disks. Data is not lost during this operation.
NOTE: On Linux, a Split Mirror cannot be performed on a mounted virtual disk. For
this reason, a Split Mirror cannot be performed on the boot drive.
To Split a Mirror:
Click Split Mirror. If you want to exit without splitting the mirror, click Go Back To Virtual Disk Page.
CAUTION: Your virtual disk will no longer be redundant after performing a Split Mirror operation.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select Split Mirror from the Available Tasks drop-down menu.
Use the Unmirror task to separate mirrored data and restore one half of the mirror to free space. Unmirroring a RAID 1 or RAID 1-concatenated virtual disk results in a single, nonredundant concatenated virtual disk. Unmirroring a RAID 10 virtual disk results in a single, nonredundant RAID 0 (striped) virtual disk. Data is not lost during this operation.
NOTE: On Linux, an Unmirror cannot be performed on a mounted virtual disk.
To Unmirror:
Click Unmirror. If you want to exit without unmirroring, click Go Back To Virtual Disk Page.
CAUTION: Your virtual disk will no longer be redundant.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select Unmirror from the Available Tasks drop-down menu.
A dedicated hot spare is an unused backup disk that is assigned to a single virtual disk. When a physical disk in the virtual disk fails, the hot spare is activated to replace the failed physical disk without interrupting the system or requiring your intervention.
Select the disk in the Connector (channel or port) table that you want to
use as the dedicated hot spare. On some controllers, more than one disk
can be selected. The disks you have selected as dedicated hot spares are
displayed in the Disks currently configured as dedicated hot spare table.
Click Apply Changes when ready.
To unassign a dedicated hot spare:
Click the disk in the Disks currently configured as dedicated hot spare
table to unassign it. Clicking the disk removes the disk from the Disks
currently configured as dedicated hot spare table and returns it to the
Connector (channel or port) table.
Click Apply Changes when ready.
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select Assign Dedicated Hot Spare or Unassign Dedicated Hot Spare
from the Available Tasks drop-down menu.
Click Execute.
Virtual Disk Task: Replace Member Disk (Step 1 of 2)
NOTE: This feature is supported only on SAS controllers with firmware versions 6.1
and later.
You can copy data from a physical disk, which is a member of a virtual disk, to another physical disk by providing a Replace Member Configuration option. You can initiate multiple copies of data from different array groups.
The source physical disk should be part of a virtual disk and in the Online state. Also, the virtual disk should not be fully degraded.
NOTE: You must also enable the Revertible Hot Spare option to use Replace
Member Disk task.
The destination physical disk should be in the Ready state, available to be written to, and of appropriate size and type.
NOTE: The destination physical disk can also be an available hot spare.
To Replace a Member Disk: (Step 1 of 2)
Select the physical disk in the Connector table that you want to replace.
Select the destination disk in the Disks available for replace member
operation table.
CAUTION: If you choose a hot spare as the destination physical disk, your virtual disk will be without a hot spare, unless you assign one.
NOTE: You can select only one source/destination physical disk at a time.
Click Apply Changes. If you want to exit without replacing the member
disk, click Go Back To Virtual Disk Page.
You can view the progress of the Replace Member Disk task on the Physical Disk Details page. For more information, see "Physical Disk Properties and Tasks."
To locate this task in Storage Management:
Expand the Storage tree object to display the controller objects.
Expand a controller object.
Select the Virtual Disks object.
Select Replace Member Disk from the Available Tasks drop-down menu.
Click Execute.
Virtual Disk Task: Replace Member Disk (Step 2 of 2)
This screen displays the summary of the attributes of the virtual disk in which you replaced the member disk. Use this screen to review your changes before completing the virtual disk Replace Member task.
To Replace a Member Disk: Step 2 of 2
Review your changes. The source Physical Disk table displays details of
the source physical disk. The destination Physical Disk table displays
details of the destination physical disk.
Click Finish to complete the replace member task. If you want to change
the replace member, click Go Back to Previous Page. If you want to exit
without making changes, click Cancel.
