Following is a list of terms used throughout this chapter:
Disk Group — A set of physical disks that are logically grouped and assigned a RAID level. Every disk group provides the overall capacity required to create one or more virtual disks.
Virtual Disk — A logical component created to enable hosts to access storage on the storage array. A virtual disk is created from the capacity available on a disk group and appears as one logical component even though it is created from more than one physical disk.
Storage Partitioning — Logical division of a storage array into entities consisting of one or more virtual disks that can be accessed by a single host or shared among hosts that are part of a host group.
Unconfigured Capacity — Physical disks that are not already assigned to a disk group.
Free Capacity — Space in a disk group that has not been assigned to a virtual disk.
Standby Hot Spare Drive — Physical disk that has been assigned as a hot spare drive and is available to take over for any failed physical disk.
In-use Hot Spare Drive — Physical disk that has been assigned as a hot spare drive and is currently taking over for a failed physical disk.
Snapshot Virtual Disk — Point-in-time image of a virtual disk in a storage array.
Snapshot Repository Virtual Disk — Virtual disk containing metadata and copy-on-write data for a particular snapshot virtual disk; automatically created when the snapshot virtual disk is created.
Consistency Check — Background operation that checks the parity of virtual disks.
Creating Disk Groups and Virtual Disks
Disk groups are created in the unconfigured capacity of a storage array, and virtual disks are created in the free capacity of a disk group. The maximum number of physical disks supported in a disk group is 30. The hosts attached to the storage array read and write data to the virtual disks.
NOTE: Before you can create virtual disks, you must first organize the physical disks into disk groups and configure host access. Then you can create virtual disks within a disk group.
NOTE: The disk group must contain physical disks of the same type. Mixing SAS and SATA II disks in a disk group is not supported.
To create a virtual disk, use one of the following methods:
Create a new disk group from unconfigured capacity. You first define the RAID level and free capacity (available storage space) for the disk group, and then you define the parameters for the first virtual disk in the new disk group.
Create a new virtual disk in the free capacity of an existing disk group. You only need to specify the parameters for the new virtual disk.
A disk group has a set amount of free capacity that was configured when the disk group was created. You can use that free capacity to subdivide the disk group into one or more virtual disks.
You can create disk groups and virtual disks using an automatic configuration procedure or using a manual configuration procedure. Automatic configuration provides the fastest method, but with limited configuration options. Manual configuration is a more involved process, but provides more configuration options.
When creating a virtual disk, consider all of the possible uses for that virtual disk, and select an appropriate capacity for those uses. For example, if a disk group has a virtual disk that stores multimedia files (which tend to be large) and another virtual disk that stores text files (which tend to be small), the multimedia file virtual disk requires more capacity than the text file virtual disk.
A disk group should be organized according to its related tasks and subtasks. For example, if you create a disk group for the Accounting Department, you can create virtual disks that match the different types of accounting performed in the department: Accounts Receivable (AR), Accounts Payable (AP), internal billing, and so forth. In this scenario, the AR and AP virtual disks probably need more capacity than the internal billing virtual disk.
NOTE: In Linux, the host must be rebooted after deleting virtual disks to reset the /dev entries.
NOTE: Before you can use a virtual disk, you must register the disk with the host systems. This process is described in
Host-to-Virtual Disk Mapping.
Automatic Configuration
If you want to set up virtual disks quickly, click the Configure tab and then click Automatic Configuration. With this option, you do not need to configure individual options for each virtual disk. When you use automatic configuration:
All available unconfigured capacity on the array is used.
All disk groups have the same RAID level.
All virtual disks have equal capacity.
The number of virtual disks created is based on the selected RAID level and available unconfigured capacity.
For a RAID level 1, 5, or 6 disk group, hot spare drives are selected automatically based on the number of drives and types of drives available in the storage array.
Manual Configuration
To create individual virtual disks or disk groups, click the Configure tab and then click Create Virtual Disks. You create one disk group and virtual disk at a time, but have control over the RAID level and capacity for each virtual disk and disk group. Use this method if you have unique capacity requirements for a disk group or virtual disk.
Creating a Disk Group and Virtual Disk From Unconfigured Capacity
Use the following procedure to manually create a disk group:
Click the Configure tab, then click Create Virtual Disks.
Select Unconfigured capacity on the Create Virtual Disks – Select
Capacity Type page, then click Next.
Select Manual on the Create Virtual Disks – Physical Disk Selection
Choices page, then click Next.
Select the RAID level for the new disk group.
To select one physical disk to add to the disk group, click the disk of your
choice in the Unselected physical disks list.
To select more than one physical disk to add to the disk group, press <Ctrl> while clicking the disks of your choice in the Unselected physical disks list.
NOTE: When adding more than one physical disk to a disk group, it is recommended to use disks with the same capacity. You can choose to use disks of differing capacities; however, the overall capacity of the disk group will be based on the smallest capacity physical disk. This means that additional capacity on larger physical disks will not be available for use.
Click Add to add the disk(s) you selected in step 5 to the Selected physical
disks list.
Click Calculate Capacity beneath the list of selected disks to see the
capacity of the disk group you are creating.
To add or remove capacity for the proposed disk group, highlight disks in
either list and click Add or Remove.
When you are satisfied with the size of the disk group, click Finish at the
bottom of the page.
On the Create Disk Groups and Virtual Disks - Complete page, click
Create a virtual disk using the new disk group, and then Yes.
Specify the size of the first virtual disk to be created in the new disk group
in the New virtual disk capacity box.
Enter a name for the virtual disk in the Name text box.
Specify the type of files that will be stored on the virtual disk. MD Storage
Manager will optimize the virtual disk based on your selection. Your
choices include:
File system (typical)
Database
Multimedia
When you are satisfied with the parameters of the virtual disk, click Next.
To map the new virtual disk to a host now, select Map now and assign a
logical unit number (LUN) to the virtual disk in the drop-down box.
To map the new virtual disk to a host later, select Map later.
Click Finish to create the new disk group and the first virtual disk in the
group.
Creating a Virtual Disk From Free Capacity
To manually create a virtual disk within an existing disk group, first decide in which disk group you want to create the new virtual disk. Then use the following procedure to create the new virtual disk:
Click the Configure tab, then click Create Virtual Disks.
Select Free capacity on the Create Virtual Disks – Select Capacity Type
page.
Click the plus sign (+) at the left of the disk group to display the virtual
disks and free capacity in the disk group.
Click the free capacity for the disk group you want to modify, and then
click Next at the bottom of the page.
Specify the size of the virtual disk to be created in the New virtual disk
capacity box.
Enter a name for the virtual disk in the Name text box.
Specify the type of files that will be stored on the virtual disk. MD Storage
Manager will optimize the virtual disk based on your selection. Your
choices include:
File system (typical)
Database
Multimedia
When you are satisfied with the parameters of the virtual disk, click Next.
To map the new virtual disk to a host now, select Map now and assign a
logical unit number (LUN) to the virtual disk in the drop-down box.
To map the new virtual disk to a host later, select Map later.
After you create virtual disks and map them to hosts, you must register the virtual disks with each host. Registration ensures the host recognizes the virtual disks.
If you plan to create multiple virtual disks, wait until you have created all the virtual disks to register them. Waiting prevents you from having to register virtual disks more than once.
Linux
NOTE: You need super-user (Linux) privileges to run the hot_add utility.
The hot_add utility is installed with the host-agent package and is run from the Linux command line. You cannot run the hot_add utility using the MD Storage Manager.
Windows
Windows automatically registers virtual disks.
NOTE: Virtual disks mapped to Windows Server 2008 hosts are marked offline by default. To bring the virtual disks online, use the Disk Management MMC (if you are using a GUI version of Windows Server 2008) or use the DiskPart utility (if you are using a Core version of Windows Server 2008).
Hot Spare Drive Protection
Hot spare drives in a storage array provide an additional level of protection in case a physical disk fails. Hot spare drives only take over for failed drives in a RAID level 1, 5, or 6 disk group. Using a hot spare drive can be an advantage because it automatically replaces a failed physical disk that is part of a disk group.
You can see whether hot spare protection is currently set by viewing the Hot Spare Physical Disks line in the Hardware Components area of the Summary tab. You can also see the number of standby and in-use hot spares. A standby hot spare drive is a physical disk that has been assigned as a hot spare drive and is available to take over for any failed physical disk. An in-use hot spare drive is a physical disk that has been assigned as a hot spare drive and is currently taking over for a failed physical disk.
Automatically Configuring Hot Spares
You can choose to allow MD Storage Manager to automatically configure hot spare drives. With automatic configuration, the controller automatically configures the number and type of hot spare drives that will provide optimal coverage for the storage array. The number and type of hot spare drives is determined based on the number, type, and capacity of physical disks in the storage array.
To add hot spare drive protection using automatic configuration:
Click the Configure tab, then click Configure Hot Spares.
To automatically assign hot spare drives, click Configure Hot Spares
(Automatic).
Click Assign.
To remove hot spare drive protection using automatic configuration:
Click the Configure tab, then click Configure Hot Spares.
Click Configure Hot Spares (Automatic).
Click Unassign.
Click OK in the dialog box.
Manually Configuring Hot Spares
You can choose to manually configure hot spare drives for the drive sets in your storage array. With manual configuration, you assign the type and capacity of hot spare protection for individual drives.
Click the Configure tab, then click Configure Hot Spares.
To manually assign hot spare drives, click Configure Hot Spares
(Manual).
In the Drive sets list, click the drive you wish to protect, then click Assign.
The Assign Hot Spares dialog box appears.
In the Assign Hot Spares dialog box, click the unassigned drive you want
to configure into a hot spare physical disk, then click OK.
NOTE: When manually configuring a hot spare physical disk, you must use a physical disk type that matches the other physical disks in the disk group. Using a SAS physical disk to replace a SATA II physical disk (or a SATA II physical disk to replace a SAS physical disk) is not supported. Also, the hot spare physical disk must be as large as or larger than the largest physical disk in the disk group.
Host-to-Virtual Disk Mapping
After you create virtual disks, you must map them to the host(s) connected to the array. When you configure host-to-virtual disk mapping, consider these guidelines:
Each virtual disk in the storage array can be mapped to only one host or host group.
Host-to-virtual disk mappings are shared between controllers in the storage array.
A unique LUN must be used by a host group or host to access a virtual disk.
Not every operating system has the same number of LUNs available.
Creating Host-to-Virtual Disk Mappings
Create host-to-virtual disk mappings by clicking the Configure tab, then clicking Create Host-to-Virtual Disk Mappings. When you click this link, the Storage Manager displays a series of pages in which you select the hosts and virtual disks to be mapped.
After you complete this configuration, verify the mapping by clicking Host-to-Virtual Disk Mappings on the Summary tab to ensure the configuration was created correctly.
Modifying and Removing Host-to-Virtual Disk Mapping
You might choose to modify or remove a host-to-virtual disk mapping for several reasons, such as an incorrect mapping or reconfiguration of the storage array. Modifying or removing a host-to-virtual disk mapping applies to both hosts and host groups.
NOTICE: Before you modify or remove a host-to-virtual disk mapping, you must stop any data access (I/O) to the virtual disks to prevent data loss.
Stop any data access (I/O) to the virtual disks.
Click the Modify tab and then click Edit Host-to-Virtual Disk Mappings.
MD Storage Manager displays a list of virtual disks and the hosts to which they are mapped.
Select the virtual disk you wish to modify by clicking its name.
To map the disk to a different host or host group, click Change located to
the right of the list.
To remove the disk mapping to a host or host group, click Remove located
to the right of the list.
Changing Controller Ownership of the Virtual Disk
If the host has a single data-path to the MD storage array, the virtual disk must be owned by the controller to which the host is connected. You must configure this storage array before you start I/O operations and after the virtual disk is created.
To assign ownership of the virtual disk to the connected controller:
Click the Modify tab and then select Change Virtual Disk
Ownership/Preferred Path.
Select the appropriate virtual disk and click Change.
Storage Partitioning
A storage partition is a logical entity consisting of one or more virtual disks that can be accessed by a single host or shared among hosts that are part of a host group. The first time you map a virtual disk to a specific host or host group, a storage partition is created. Subsequent virtual disk mappings to that host or host group do not create another storage partition.
One storage partition is sufficient if:
Only one attached host accesses all of the virtual disks in the storage array.
All attached hosts share access to all of the virtual disks in the storage array. When you choose this type of configuration, all of the hosts must have the same operating system and special software (such as clustering software) to manage virtual disk sharing and accessibility.
More than one storage partition is required if:
Specific hosts must access specific virtual disks in the storage array.
Hosts with different operating systems are attached to the same storage array. In this case, a storage partition will be created for each host type.
NOTE: If Microsoft Windows is the host server, you must partition and format the virtual disk using the Microsoft Management Console (MMC). Go to Settings ® Control Panel ® Administrative Tools, or Control Panel ® Administrative Tools and select the DiskManagement MMC option to format and partition the disk. If the host server is running Windows Server 2008 Core version, partition and format the virtual disk using the Microsoft DiskPart utility.
Disk Group and Virtual Disk Expansion
Adding free capacity to a disk group is achieved by adding unconfigured capacity on the array to the disk group. Data is accessible on disk groups, virtual disks, and physical disks throughout the entire modification operation. The additional free capacity can then be used to perform a virtual disk expansion on a standard or snapshot repository virtual disk.
Disk Group Expansion
To add free capacity to a disk group, use the following procedure:
Click the Modify tab, then click Add Free Capacity (Physical Disks).
On the Add Free Capacity page, click the disk group you want to expand.
Click Next beneath the list of disk groups.
The Storage Manager displays information on the disk group you selected.
In the Add capacity to disk group drop-down menu, choose the amount of
unconfigured capacity to add to the disk group.
Click Finish to start the process of adding capacity to the disk group.
You can also use the Command Line Interface (CLI) on both Windows and Linux hosts to add free capacity to a disk group. See the CLI Guide for more information.
Once the capacity expansion is completed, additional free capacity is available in the disk group for creation of new virtual disks or expansion of existing virtual disks.
Virtual Disk Expansion
Virtual disk expansion is a dynamic modification operation that increases the capacity of standard virtual disks.
NOTE: Snapshot repository virtual disks can be expanded from the CLI or from MD Storage Manager. All other virtual disk types are expandable only from the CLI.
If you receive a warning that the snapshot repository virtual disk is becoming full, you may expand the snapshot repository virtual disk from MD Storage Manager. See Snapshot Repository Capacity for step-by-step instructions.
Disk Group Migration
Disk group migration allows you export a disk group so that you can import the disk group to a different storage array. You can also export a disk group so that you can store the data offline.
NOTE: During the export process (before the disk group is imported) you will lose access to the data on the exported disk group.
NOTE: You must export a disk group before you move the disk group or import the disk group.
Export Disk Group
The export disk group operation prepares the physical disks in the disk group for removal. You can remove the physical disks for offline storage, or you can import the disk group to a different storage array. After you complete the export disk group operation, all of the physical disks are offline. Any associated virtual disks or free capacity nodes are no longer shown in the MD Storage Manager Software.
Non-Exportable Components
You must remove or clear any non-exportable settings before you can complete the export disk group procedure. Remove or clear the following settings:
Persistent reservations
Host-to-virtual disk mappings
Virtual disk copy pairs
Snapshot virtual disks and snapshot repository virtual disks
Remote mirror pairs
Mirror repositories
Basic Steps for Exporting a Disk Group
On the source storage array:
Save the storage array configuration.
Stop all I/O, and unmount or disconnect the file systems on the virtual
disks in the disk group.
Back up the data on the virtual disks in the disk group.
Locate the disk group, and label the physical disks.
Place the disk group offline.
Obtain blank physical disk modules or new physical disks.
On the target storage array:
Verify that the target storage array has available physical disk slots.
Verify that the target storage array supports the physical disks that you will
import.
Verify that the target storage array can support the new virtual disks.
Verify that the latest version of firmware is installed on the RAID
controller module.
Import Disk Group
The import disk group operation adds the imported disk group to the target storage array. After you complete the import disk group operation, all of the physical disks have Optimal status. Any associated virtual disks or free capacity nodes are now shown in the MD Storage Manager Software installed on the target storage array.
NOTE: You will lose access to your data during the export/import process.
NOTE: You must export a disk group before you move the disk group or import the disk group.
Basic Steps to Import a Disk Group
NOTE: You must insert all of the physical disks that are part of the disk group into the enclosure before the disk group can be imported.
On the target storage array:
Insert the exported physical disks into the available physical disk slots.
Review the Import Report for an overview of the disk group that you are
importing.
Check for non-importable components.
Confirm that you want to proceed with the import procedure.
NOTE: Some settings cannot be imported during the import disk group procedure.
The following settings are removed/cleared during the procedure:
Persistent reservations
Host-to-virtual disk mappings
Virtual disk copy pairs
Snapshot virtual disks and snapshot repository virtual disks
Remote mirror pairs
Mirror repositories
Storage Array Media Scan
The media scan is a long-running operation that examines virtual disks to verify that data is accessible. The process finds media errors before normal read and write activity is disrupted and reports errors to the event log.
Errors discovered by the media scan include:
Unrecovered media error — Data could not be read on the first attempt or on any subsequent attempts. For virtual disks with redundancy protection, data is reconstructed, rewritten to the physical disk, and verified and the error is reported to the event log. For virtual disks without redundancy protection (RAID 1, RAID 5, and RAID 6 virtual disks), the error is not corrected but is reported to the event log.
Recovered media error — Data could not be read by the physical disk on the first attempt but was successfully read on a subsequent attempt. Data is rewritten to the physical disk and verified and the error is reported to the event log.
Redundancy mismatches error — The first 10 redundancy mismatches that are found on the virtual disk are reported to the event log.
Unfixable error — Data could not be read and parity or redundancy information could not be used to regenerate the data. For example, redundancy information cannot be used to reconstruct the data on a degraded virtual disk. The error is reported to the event log.
Changing Media Scan Settings
Click the Tools tab, then click Change Media Scan Settings.
Select the number of days allowed for the media scan to complete in the
Scan duration (days) box.
NOTE: Performing the media scan frequently may negatively impact the performance of other operations. Adjust scan duration based on the performance needs of your storage array.
In the Select virtual disks to scan box, click the virtual disk you want to
include in the media scan.
NOTE: Press <Ctrl> and click to add more than one virtual disk to the media scan. Click Select All to include all virtual disks in the media scan.
Check the Scan selected virtual disks checkbox to enable scanning, then
choose either With consistency check or Without consistency check.
Consistency check enables parity data to be checked during the media scan.
Click OK to accept the updated media scan settings.
Suspending the Media Scan
You cannot perform a media scan while performing another long-running operation on the disk drive such as reconstruction, copy-back, reconfiguration, virtual disk initialization, or immediate availability formatting. If you want to perform another long-running operation, you should suspend the media scan.
NOTE: A background media scan is the lowest priority of the long-running operations.
Click the Tools tab, then click Change Media Scan Settings.
Check the Suspend media scan checkbox.
Click OK to suspend media scanning.
Microsoft Services
Virtual Disk Service
The Microsoft Virtual Disk Service (VDS) is supported on your RAID storage array. Microsoft VDS is a set of application programming interfaces (APIs) that provides a single interface for managing disks and other storage hardware, including creating virtual disks on those physical disks.
Volume Shadow-Copy Service
The Microsoft Volume Shadow-copy Service (VSS) is a storage management interface for Microsoft Windows operating systems. VSS enables your storage array to interact with third-party applications that use the VSS Application Programming Interface.
Virtual disks that will be used as source virtual disks for VSS snapshots should have names no longer than 16 characters. The VSS hardware provider uses the source virtual disk name as a prefix for the snapshot and repository virtual disk names. The resulting snapshot and repository names will be too long if the source virtual disk name exceeds 16 characters.
For more information on VDS and VSS, see www.microsoft.com.
