NOTICE: A virtual disk copy overwrites data on the target virtual disk. Before starting a virtual disk copy, ensure that you no longer need the data or back up the data on the target virtual disk.
NOTE: If you ordered this feature, you received a Premium Feature Activation card that shipped in the same box as your Dell PowerVault MD storage array. Follow the directions on the card to obtain a key file and to enable the feature.
NOTE: The basic virtual disk copy feature allows up to four virtual disk copies to be present at the same time. If the enhanced snapshot and virtual disk copy premium feature was ordered, then up to eight snapshot/virtual disk copies may be present at the same time.
NOTE: The preferred method for creating a virtual disk copy is to copy from a snapshot virtual disk. This allows the original virtual disk used in the snapshot operation to remain fully available for read/write activity while the snapshot is used as the source for the virtual disk copy operation.
When you create a virtual disk copy, you create a copy pair that has a source virtual disk and a target virtual disk on the same storage array.
The source virtual disk is the virtual disk that contains the data you want to copy. The source virtual disk accepts the host I/O read activity and stores the data until it is copied to the target virtual disk. The source virtual disk can be a standard virtual disk, a snapshot virtual disk, or the source virtual disk of a snapshot virtual disk. When you start a virtual disk copy, all data is copied to the target virtual disk, and the source virtual disk permissions are set to read-only until the virtual disk copy is complete.
The target virtual disk is a virtual disk to which you copy data from the source virtual disk. The target virtual disk can be a standard virtual disk, or the source virtual disk of a failed or disabled snapshot virtual disk.
After the virtual disk copy is complete, the source virtual disk becomes available to host applications for write requests. To prevent error messages, do not attempt to access a source virtual disk that is participating in a virtual disk copy while the virtual disk copy is in progress.
Reasons to use virtual disk copy include the following:
Copying data for improved access — As your storage requirements for a virtual disk change, you can use a virtual disk copy to copy data to a virtual disk in a disk group that uses drives with larger capacity within the same storage array. Copying data for larger access capacity enables you to move data to greater capacity physical disks (for example, 61 GB to 146 GB).
Restoring snapshot virtual disk data to the source virtual disk — The Virtual Disk Copy feature enables you first to restore the data from a snapshot virtual disk and then to copy the data from the snapshot virtual disk to the original source virtual disk.
Creating a backup copy — The Virtual Disk Copy feature enables you to create a backup of a virtual disk by copying data from one virtual disk (the source virtual disk) to another virtual disk (the target virtual disk) in the same storage array, minimizing the time that the source virtual disk is unavailable to host write activity. You can then use the target virtual disk as a backup for the source virtual disk, as a resource for system testing, or to copy data to another device, such as a tape drive or other media.
NOTE: Recovering from a backup copy — You can use the Edit Host-to-Virtual Disk Mappings feature to recover data from the backup virtual disk you created in the previous procedure. The Mappings option enables you to unmap the source virtual disk from its host and then to map the backup virtual disk to the same host.
Creating a Virtual Disk Copy for an MSCS Shared
Disk
To create a virtual disk copy for a Microsoft Cluster Server (MSCS) shared disk, create a snapshot of the virtual disk, and then use the snapshot virtual disk as the source for the virtual disk copy.
NOTE: An attempt to directly create a virtual disk copy for an MSCS shared disk, rather than using a snapshot virtual disk, will fail with the following error: The operation cannot complete because the selected virtual disk is not a source virtual disk candidate.
NOTE: When creating a snapshot virtual disk, map the snapshot virtual disk to only one node in the cluster. Mapping the snapshot virtual disk to the host group or both nodes in the cluster may cause data corruption by allowing both nodes to concurrently access data.
Virtual Disk Read/Write Permissions
After the virtual disk copy is complete, the target virtual disk automatically becomes read-only to the hosts. The target virtual disk rejects read and write requests while the virtual disk copy operation has a status of Pending or In Progress or if the operation fails before completing the copy. Keep the target virtual disk Read-Only enabled if you want to preserve the data on the target virtual disk for reasons such as the following:
If you are using the target virtual disk for backup purposes.
If you are using the data on the target virtual disk to copy back to the source virtual disk of a disabled or failed snapshot virtual disk.
If you decide not to preserve the data on the target virtual disk after the virtual disk copy is complete, change the write protection setting for the target virtual disk to Read/Write.
To set the target virtual disk read/write permissions, complete the following steps:
Click the Modify tab, and then click Manage Virtual Disk Copies.
Select one or more copy pairs in the table and click Permissions to the
right of the table.
The Set Target Virtual Disk Permissions dialog box appears.
In the Set Target Virtual Disk Permissions dialog box select either Read-
Only or Read/Write.
Click OK in the dialog box.
If you select Read-Only, write requests to the target virtual disk will be rejected. If you select Read/Write, the host can read and write to the target virtual disk after the virtual disk copy is complete.
Virtual Disk Copy Restrictions
Before you perform any virtual disk copy tasks, understand and adhere to the restrictions listed in this section. The restrictions apply to the source virtual disk, the target virtual disk, and the storage array.
While a virtual disk copy has a status of In Progress, Pending, or Failed, the source virtual disk is available for read I/O activity only. After the virtual disk copy is complete, read and write I/O activity to the source virtual disk are permitted.
A virtual disk can be selected as a target virtual disk for only one virtual disk copy at a time.
A virtual disk copy for any virtual disk cannot be mounted on the same host as the source virtual disk.
Windows does not allow a drive letter to be assigned to a virtual disk copy.
A virtual disk with a Failed status cannot be used as a source virtual disk or target virtual disk.
A virtual disk with a Degraded status cannot be used as a target virtual disk.
A virtual disk participating in a modification operation cannot be selected as a source virtual disk or target virtual disk. Modification operations include the following:
Capacity expansion
RAID-level migration
Segment sizing
Virtual disk expansion
Defragmenting a virtual disk
NOTE: The following host preparation sections also apply when using the virtual disk copy feature through the CLI interface.
Creating a Virtual Disk Copy
Use the Create Virtual Disk Copies feature on the Configure tab to create a full copy of a source virtual disk. This operation overwrites any existing data on the target virtual disk. Once the virtual disk copy has started, all I/O activity to the source virtual disk is read-only. Any attempts to write to the source virtual disk fail until the operation is complete.
NOTE: It is recommended that you create a virtual disk copy from a snapshot virtual disk rather than from the original virtual disk. This allows the original virtual disk to remain in full use while the snapshot of this virtual disk is used as the source for the virtual disk copy operation.
Preparing Host Servers to Create a Virtual Disk Copy
NOTICE: Before you create a new copy of a source virtual disk, stop any data access (I/O) activity or suspend data transfer to the source virtual disk (and, if applicable, the target disk) to ensure that you capture an accurate point-in-time image of the source virtual disk. Close all applications, including Windows Internet Explorer, to make sure all I/O activity has stopped.
NOTE: Removing the drive letter of the associated virtual disk(s) in Windows or unmounting the virtual drive in Linux will help to guarantee a stable copy of the drive for the virtual disk copy.
Before creating a virtual disk copy, both the host server and the associated virtual disk you are copying have to be in the proper state. Perform the following steps to prepare your host server and virtual disk:
Stop all I/O activity to the source and target virtual disk.
Using your Windows system, flush the cache to both the source and the
target virtual disk (if mounted). At the host prompt, type
Click the Summary tab, then click Disk Groups & Virtual Disks to ensure
that the virtual disk is in Optimal or Disabled status.
Remove the drive letter(s) of the source and (if mounted) virtual disk in
Windows or unmount the virtual drive(s) in Linux to help guarantee a
stable copy of the drive for the virtual disk. If this is not done, the copy
operation will report that it has completed successfully, but the copied
data will not be updated properly.
Follow any additional instructions for your operating system. Failure to
follow these additional instructions can create unusable virtual disk copies.
NOTE: If your operating system requires additional instructions, you can find those instructions in your operating system documentation.
Copying the Virtual Disk
After first preparing the host server(s) as specified in the preceding procedure, complete the following steps to make a virtual disk copy:
Click the Configure tab, then click Create Virtual Disk Copies.
On the Select Source Virtual Disk page, select the virtual disk to copy
(source virtual disk), and click Next.
The Select Target Virtual Disk page appears.
NOTE: If the virtual disk you select is not valid, an information dialog box appears explaining the types of virtual disks you can use as the source for a virtual disk copy. Click OK to close this dialog box and select a different source virtual disk.
Choose the target virtual disk:
To use an existing virtual disk as the target, select Use an existing
virtual disk and highlight the virtual disk of your choice in the list.
NOTE: If you select a target virtual disk with a capacity similar to the source virtual disk, you reduce the risk of having unusable space on the target virtual disk after the virtual disk copy is completed.
To create a new virtual disk for the target, select Create a new virtual
disk. Type a name for this new target virtual disk in the text box.
Click Next at the bottom of the page.
The Create virtual disk copies—Set Copy Priority dialog box appears.
Set the copy priority for the virtual disk copy and click Next.
The source virtual disk, the target virtual disk, and the copy priority setting that you selected appear on the Create virtual disk copies—Confirm Copy Settings dialog. The higher priorities allocate more resources to the virtual disk copy at the expense of the storage array's performance. For more information, see Setting Copy Priority.
Storage Array Performance During Virtual Disk
Copy
The following factors contribute to the overall performance of the storage array:
I/O activity
Virtual disk RAID level
Virtual disk configuration — Number of drives in the virtual disk groups
Virtual disk type — Snapshot virtual disks might take more time to copy than standard virtual disks
During a virtual disk copy, resources for the storage array are diverted from processing I/O activity to completing a virtual disk copy. This affects the overall performance of the storage array. When you create a new virtual disk copy, you define the copy priority to determine how much controller processing time is diverted from I/O activity to a virtual disk copy operation.
Setting Copy Priority
The Copy Priority setting defines how much of the storage array's resources are used to complete a virtual disk copy, rather than to fulfill I/O requests. Changing the copy priorities sets the rate at which a virtual disk copy is completed.
Five copy priority rates are available: lowest, low, medium, high, and highest. If the copy priority is set at the lowest rate, I/O activity is prioritized and the virtual disk copy takes longer. At the highest priority rate, the virtual disk copy is prioritized, and I/O activity for the storage array is slower.
You can change the copy priority for a virtual disk copy in the following circumstances:
Click the Modify tab, then click Manage Virtual Disk Copies. Select an active copy operation, then click Priority to the right of the list of virtual disk copies.
When re-creating a virtual disk copy
Click the Modify tab, then click Manage Virtual Disk Copies. Select a completed copy operation, then click Re-copy to the right of the list of virtual disk copies.
Stopping a Virtual Disk Copy
You can stop a virtual disk copy operation that has an In Progress status, a Pending status, or a Failed status. Stopping a virtual disk copy that has a Failed status clears the Needs Attention status displayed for the storage array.
When you stop a virtual disk copy, all mapped hosts have write access to the source virtual disk. If data is written to the source virtual disk, the data on the target virtual disk no longer matches the data on the source virtual disk.
To stop a virtual disk copy, complete the following steps:
Click the Modify tab, and then click Manage virtual disk copies.
Select the copy operation you wish to stop by clicking it and click Stop.
You can only select one copy operation at a time to be stopped.
Click Yes to stop the virtual disk copy.
Recopying a Virtual Disk
You can recopy a virtual disk when you have stopped a virtual disk copy and you want to start it again or when a virtual disk copy has failed.
The Recopy option overwrites existing data on the target virtual disk and makes the target virtual disk read-only to hosts. This option fails all snapshot virtual disks associated with the target virtual disk, if any exist.
Preparing Host Servers to Recopy a Virtual Disk
NOTICE: Before you create a new copy of a source virtual disk, stop any data access (I/O) activity or suspend data transfer to the source virtual disk (and, if applicable, the target disk) to ensure that you capture an accurate point-in-time image of the source virtual disk. Close all applications, including Windows Internet Explorer, to make sure all I/O activity has stopped.
NOTE: Removing the drive letter of the associated virtual disk(s) in Windows or unmounting the virtual drive in Linux will help to guarantee a stable copy of the drive for the virtual disk copy.
Before creating a new virtual disk copy for an existing copy pair, both the host server and the associated virtual disk you are recopying have to be in the proper state. Perform the following steps to prepare your host server and virtual disk:
Stop all I/O activity to the source and target virtual disk.
Using your Windows system, flush the cache to both the source and the
target virtual disk (if mounted). At the host prompt, type
Click the Summary tab, then click Disk Groups & Virtual Disks to ensure
that the virtual disk is in Optimal or Disabled status.
Remove the drive letter(s) of the source and (if mounted) virtual disk in
Windows or unmount the virtual drive(s) in Linux to help guarantee a
stable copy of the drive for the virtual disk. If this is not done, the copy
operation will report that it has completed successfully, but the copied
data will not be updated properly.
Follow any additional instructions for your operating system. Failure to
follow these additional instructions can create unusable virtual disk copies.
NOTE: If your operating system requires additional instructions, you can find those instructions in your operating system documentation.
Recopying the Virtual Disk
After first preparing the host server(s) as specified in the preceding procedure, complete the following steps to create a new virtual disk copy for an existing copy pair:
Click the Modify tab, and then click Manage virtual disk copies.
You can only select one copy operation at a time to be recopied.
Select the copy operation in the list displayed by the Manage Virtual Disk
Copies page, and then click Recopy at the right of the list.
The Recopy dialog box appears. Set the copy priority.
Type yes, and click OK.
If you approve of the parameters, type yes in the text box and
click Finish to confirm the copy settings and start the virtual disk copy.
The Copy Started page appears, verifying that the virtual disk copy has started. This dialog also enables you to exit the Create virtual disk copies feature or create another new virtual disk copy.
Choose one of the following options, based on whether you want to create
another virtual disk copy or modify the one you just created:
Yes — Create a new virtual disk copy.
No — Exit the Create virtual disk copies dialog.
Manage Virtual Disk Copies — Recopy, stop the copy process, set permissions or priority, or remove virtual disk copies.
You can view the progress of a virtual disk copy in the Manage virtual disk copies page. For each copy operation in progress, the list displays a sliding scale in the Status field showing the percentage of the operation that is complete.
Once the virtual disk copy is complete, perform the following actions:
In Linux, if you created the target virtual disk with unconfigured capacity,
run the hot_add utility.
If you created the target virtual disk with unconfigured capacity, you must
map the virtual disk to a host in order to use it. See Host-to-Virtual Disk
Mapping for more information.
You must register the target virtual disk with the operating system before
you can use the new virtual disk. Perform the following steps:
Enable write permission on the target virtual disk by either removing
the virtual disk copy pair (see Removing Copy Pairs) or explicitly
setting write permission.
In Windows, assign a drive letter to the virtual disk.
NOTE: Following a disk copy, if the properties of a Windows-based volume indicate a RAW file system (one that has not been formatted) you must reboot the system so that Windows can recognize the correct virtual target disk.
In Linux, mount the virtual disk.
Enable I/O activity to the source virtual disk and the target virtual disk.
Removing Copy Pairs
Removing copy pairs permanently removes any virtual disk copy–related information for the source virtual disk and target virtual disk in the Virtual Disk Properties and the Storage Array Profile dialogs.
After you remove the virtual disk copy, you can select the target virtual disk as a source virtual disk or a target virtual disk for a new virtual disk copy. Removing a virtual disk copy also permanently removes the Read-Only attribute for the target virtual disk.
Removing copy pairs does not delete the data on the source virtual disk or target virtual disk. This merely breaks the copy relationship between the two virtual disks.
When you remove a virtual disk copy from the storage array, the target write attribute for the target virtual disk is also removed. If the virtual disk copy is in In Progress status, you must stop the virtual disk copy before you can remove the copy pair.
To remove a copy pair, perform the following steps:
Click the Modify tab, and then click Manage virtual disk copies.
Select one or more copy pairs in the table, and click Remove.
