Continuous Data Protection Operations

In this topic:

Rollback operations

Enabling/disabling CDP and changing settings

Creating rollbacks

Reverting from rollbacks

Splitting rollbacks

Deleting rollbacks

Changing the location and maximum size of the history log

Also see:

Rollback Details

CDP and Rollback Status

Virtual Disk Groups for information when performing rollback operations on groups.

System Health Thresholds to set history log size and retention period thresholds.

Rollback Operations
Create a rollback	Creates a logical image of the data residing on a CDP-enabled virtual disk at a selected point in time. (After you create the rollback, you can perform additional operations on the rollback.) See Creating Rollbacks.
Revert from rollback	Resynchronizes the CDP-enabled virtual disk and the selected rollback, so that the CDP-enabled virtual disk becomes an image of the current state of the rollback. See Reverting from Rollbacks.
Split rollback	Terminates the relationship between the CDP-enabled virtual disk and the rollback virtual disk. The data on the rollback is preserved. After the operation is complete, the rollback virtual disk becomes a fully usable single virtual disk and is no longer designated as a rollback virtual disk. See Splitting Rollbacks.
Delete rollback	Deletes the rollback virtual disk and leaves the CDP-enabled virtual disk intact. See Deleting Rollbacks.

Rollback operations can be performed from:

• The Virtual Disk Details page>Rollbacks tab.
• The context menu in the DataCore Servers Panel, Hosts Panel, or Virtual Disks List.

Before enabling Continuous Data Protection (CDP) on a virtual disk, see Continuous Data Protection (CDP) for important notes and best practices.

Enabling or Disabling CDP

CDP can be enabled when creating the virtual disk or any time after. The following instructions are for enabling or disabling the feature after the virtual disk is created.

Enabling CDP After Virtual Disk Creation

1. If enabling CDP on a single virtual disk, it must be unserved from hosts.
2. In the Virtual Disk Details page>Settings tab, click Advanced Options.

   (This operation can also be initiated using the context menu from the panels and any virtual disk list.)

3. Select the Continuous Data Protection Enabled check box.
4. In DataCore Server and Disk Pool, select the DataCore Server and disk pool where the history log should be created.
5. In Maximum history log size, select the maximum log size.
6. Click Apply.

If the enabled virtual disk is mirrored, as data is received from the host, at times the allocation size of the virtual disk on the DataCore Servers may be different. This is expected behavior when CDP is enabled.

Disabling CDP

The following three screenshots show the progression of a virtual disk being disabled in the details page>Info tab. During the process, status will be "Disabling" and a progress bar is displayed. When data protection is completed, the status will be displayed momentarily as "Disabled", then all data protection information will be removed from the Info tab.

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To disable CDP after virtual disk creation:

1. In the Virtual Disk Details page>Settings tab, click Advanced Options.
2. Clear the Continuous Data Protection Enabled check box.
3. Click Apply.

Creating Rollbacks

A rollback is a logical copy of a CDP-enabled virtual disk created at a chosen point-in-time (restore point). Rollbacks can be created at various restore points, served to hosts and viewed to determine the validity of the data. The rollback containing the optimal image of data can be used to restore the lost or damaged data.

To create a rollback:

1. In the Virtual Disk Details page>Rollbacks tab, click the link Create rollback to open the Create Rollback dialog box. (This operation can also be initiated from the Ribbon or via the context menu from the panels and any virtual disk list.)
2. In the dialog box, a default name is provided for the rollback. The default consists of the name of the source virtual disk and timestamp. Replace the name and enter a description if desired.
3. Select the Restore Point. The rollback will be a logical representation of data at the chosen point-in-time.
   • The slide bar represents the history log time period. When you move the slide bar, the time is reflected in the Restore Point field.
   • In the Restore Pointfield, the time can be changed by selecting or entering the date and time.
4. The rollback can only exist on one server, usually the server with the history log. If a rollback is being created on a virtual disk group consisting of virtual disks from more than one server and different members have CDP enabled, select the DataCore Server where the rollback should be created.
5. Choose the rollback type, which determines the action to take for this rollback in the event that the history log advances past the restore point.

   This setting cannot be changed after the rollback is created.

   • Select Expire rollback to allow the rollback to automatically expire as the restore point reaches the end of the history log. The rollback will expire without warning and be permanently unusable; it should then be deleted.
   • Select Persistent rollback to keep the rollback accessible until the rollback is manually deleted or split. Keeping a rollback persistent can have ramifications. In order to keep the rollback accessible, when the restore point reaches the end of the history log it will not be destaged, therefore, a mirrored virtual disk will have compromised mirror redundancy and a single virtual disk will become inaccessible. In this case, the rollback will have to be manually deleted or split to resume writes to the CDP-enabled virtual disk on the server with the history log.
6. In Storage Profile, select the storage profile of the rollback. (The default setting is Normal, which may be different from the CDP-enabled virtual disk. See Storage Profiles for more information.)
7. Only select the Duplicate disk identifier check box if both source virtual disk and rollback will be served to hosts requiring the same SCSI inquiry ID (virtual product information). For instance, this is required for ESX clusters.
8. Select the Assign ownership to me check box to assign exclusive ownership to the user account currently logged in and creating the rollback. This restricts all operations on the rollback to only the account logged in and the Administrator account.
9. In the pool list, select the pool to use to create the rollback.
10. Click Create.

If unsure of the accurate point-in-time to select, create several rollbacks with various restore points. Then serve the rollbacks to the host and determine the best rollback to use to either revert the data to an acceptable state or split the rollback to a fully usable virtual disk.

After creating a rollback:

• You can monitor the status in the Virtual Disk Details page>Rollbacks tab. Current history log retention period and history log allocated space for the source virtual disk is provided in the Virtual Disk Details page>Info tab.
• The rollback is listed in DataCore Servers Panel under Virtual Disks and in the Virtual Disks List. (The rollback will appear under the selected server.)
• A Rollback Details page is created for the rollback.

Reverting from Rollbacks

Resynchronizes the CDP-enabled virtual disk and the selected rollback, so that the CDP-enabled virtual disk becomes an image of the current state of the rollback, including any changes made to the rollback.

Before this command is performed, I/O should be stopped and the CDP-enabled virtual disk should be unserved from the host. This command causes a full copy from the rollback to the CDP-enabled virtual disk. Reverting will overwrite all changes that have occurred on the CDP-enabled virtual disk after the restore point.

The revert command cannot be performed on a CDP-enabled virtual disk that is:

• Served to a host

  Before this command is performed, I/O operations should be stopped and the virtual disk should be unserved from the host.

• Mirrored; the mirrored virtual disk must be split first.
• The source of a snapshot; snapshots must be deleted or split first.
• The source of a replication; replications must be split first.

To revert from the rollback:

1. Prepare the CDP-enabled virtual disk to be reverted:
   1. Stop I/O operations from the host and unserve the CDP-enabled virtual disk.
   2. Split mirrored virtual disks, delete replications, delete snapshots.
2. In the Virtual Disk Details page>Rollbacks tab, right-click on the rollback with the restore point to which you want to revert and select Revert from Rollback.
3. Click Yes on the confirmation message.
4. After the revert operation is complete, serve the CDP-enabled virtual disk to the host again and resume I/O operations.
5. Delete all rollbacks created from the CDP-enabled virtual disk.

Splitting Rollbacks

Terminates the relationship between the CDP-enabled virtual disk and the rollback virtual disk. The data on the rollback is preserved. After the operation is complete, the rollback virtual disk becomes a fully usable single virtual disk and is no longer designated as a rollback virtual disk.

When a rollback group is split, a new virtual disk group will be created and the resulting virtual disks will be added to the new group.

Use caution when a virtual disk is using duplicate disk IDs and is involved with CDP. If the rollback is split, both virtual disks will have the same SCSI device ID. Under these circumstances, the SCSI device ID for one virtual disk may need to be changed in order to make it unique. See SCSI Standard Inquiry Data.

To split the rollback:

1. In the Virtual Disk Details page>Rollbacks tab, right-click on the rollback that you want to use to recover data and select Split Rollback.
2. Click Yes on the confirmation message. After the split operation is complete, the rollback becomes a fully usable virtual disk.

   The virtual disk is no longer enabled for CDP, so enable the option if required.

3. Delete all rollbacks created from the original CDP-enabled virtual disk.

Changing the Location and Size of the History Log

Every CDP-enabled virtual disk has a log that contains the history of data changes. The history log is contained in a designated disk pool on a specified DataCore Server.

Changing Location

The location (DataCore Server and/or disk pool) of the history log is set at the time that CDP is enabled. In order to change the location on virtual disks that have CDP enabled, the feature must be disabled first, and then re-enabled after the location has been changed.

To change the location of the history log of a virtual disk with CDP enabled:

1. In the Virtual Disk Details page>Settings tab, click Advanced Options.
2. Clear the Continuous Data Protection Enabled check box and click Apply.
3. A warning will appear that disabling Continuous Data Protection can take a long time. Click YES to continue.
4. Wait until CDP has been completely disabled. This can take a considerable amount of time. Progress can be monitored in the Virtual Disk Details page>Info tab.

   The following three screenshots show the progression of a virtual disk being disabled in the details page>Info tab. During the process, status will be "Disabling" and a progress bar is displayed. When data protection is completed, the status will be displayed momentarily as "Disabled", then all data protection information will be removed from the Info tab.

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5. When CDP is completely disabled, in the Settings tab, select the Continuous Data Protection Enabled check box.
6. The history log settings will become available:
   1. In DataCore Server, select the DataCore Server where the history log should be created.
   2. In Disk Pool, select the disk pool where the history log should be created.
   3. In Maximum history log size, enter the maximum log size. When the maximum size of the history log is encroached, the oldest data changes in the history log will be destaged to make room for new data changes.
7. Click Apply.

Changing Size

The desired maximum size of the history log for the CDP-enabled virtual disk can be changed, but cannot be smaller than the currently allocated size as displayed in the Virtual Disk Details page>Info tab (see History log).

Use caution when decreasing the desired maximum history log size of the CDP-enabled virtual disk. The retention period for a virtual disk is defined by the licensed retention time and maximum history log size for the source virtual disk. The amount of write I/Os for the virtual disk will determine how fast the history log will reach maximum size. The retention period for the history log is provided in the Virtual Disk Details>Info Tab (see Retention period).

Since the history log retention period will fluctuate based on the amount of I/Os written to the virtual disk, the retention period should only be used as a guideline.

When the history log size exceeds 90% of the maximum size, the write I/O rate to the virtual disk will be throttled so that the log can be destaged faster than the incoming I/O.

To change the desired maximum size of the history log:

1. In the Virtual Disk Details page>Settings tab, click Advanced Options.
2. In the Continuous Data Protection area, change the value in the Desired maximum history log size field.
3. Click Apply.

Deleting Rollbacks

To delete a rollback:

1. In the Virtual Disk Details page>Rollbacks tab, right-click the rollback and select Delete.
2. A confirmation message appears; read the message. To continue with the operation, click the check box, then click Yes.