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12 TimeMark, CDP, and TimeView
Displaying the TimeMark Information of a Logical Resource
Modifying the TimeMark Properties
Adding a Mirror for a CDP Journal
Assigning a TimeView to Clients
Rolling Back a Logical Resource
The IX3000 provides the TimeMark function to help you protect mission-critical data. The function enables you to recover data back from a previous point in time. With TimeMark, you can guard against soft errors, non-catastrophic data loss, including inadvertent deletion of files and data corruption caused by software errors or viruses.
TimeMark features the following:
l Applicable to most logical resources, including SAN resources, replica disks, and groups.
l Supporting both automatic and manual TimeMark creation.
l Supporting data rollback, which can restore data to its healthy state at a given point in time quickly.
l Supporting TimeMark copy, with which you can create a real and permanent resource from any existing TimeMark. Thus, you can get the same data as it was when the TimeMark was created.
l Supporting up to 255 TimeMarks for each logical resource. When the maximum number of TimeMarks is reached, newly created TimeMarks will overwrite the oldest ones.
While TimeMarks tracks changes to specific points in time, continuous data protection (CDP), used in conjunction with TimeMark, allows data roll-back to any point in time within the protected time range and thus provides stronger data protection.
Figure 12-1 shows the data protection and recovery process of CDP.
Figure 12-1 Schematic diagram for CDP
The TimeView feature is an extension of the TimeMark function. It allows you to mount a TimeMark as a virtual drive for retrieval of the files at the specific point in time. You can assign the virtual drive to multiple SAN clients for concurrent, independent processing of data, while the original data set is still actively being accessed or updated by the primary SAN client.
When you want to restore individual files from a drive, you can use TimeView to mount the desired TimeMark as a virtual drive and then copy the desired files to your original virtual drive. Compared with rolling back the entire drive to a point in time, TimeView improves efficiency.
TimeView is different from TimeMark copy in that:
l The target resource generated by TimeView is a virtual resource and thus does not use disk space.
l Creating a TimeView is faster than creating a TimeMark copy.
l The target resource generated by the TimeMark copy option is a real and permanent resource, which requires the same disk space size as the original resource does.
l Do not use the virtual drive mounted for a TimeView as the working drive or write data to the TimeView. Doing so can cause anomalies such as data loss.
l You cannot configure any storage services on a virtual drives mounted for a TimeView.
Because the initial TimeMark is created based on the system time of the console PC while subsequent TimeMarks are created based on the system time of the NeoStor server, make sure that the system time settings of the console PC and the NeoStor servers are synchronized to avoid anomalies.
You can specify the initial TimeMark creation time in the window shown in Figure 12-14.
When working with TimeMark, you can perform these tasks:
l Creating a TimeMark Manually
l Displaying the TimeMark Information of a Logical Resource
l Modifying the TimeMark Properties
The system can create TimeMarks according to your storage policy. Additionally, you can create TimeMarks manually as needed.
To create a TimeMark manually, follow these steps:
Step1 Right-click the desired logical resource with TimeMark enabled.
Step2 Select TimeMark > Create from the shortcut menu. A dialog box appears, as shown in Figure 12-2.
Figure 12-2 Create a TimeMark manually
Step3 Add a comment for the TimeMark for the ease of future retrieval and management as needed.
Step4 Set a priority for the TimeMark, which can be Low, Medium, High, and Critical.
When the maximum number of TimeMarks is reached, the system deletes the oldest TimeMarks based on priority.
Step5 Select to enable snapshot notification for the TimeMark.
Snapshot notification collaborates with client software to notify the SAN client of coming snapshot actions. This allows the SAN client to take action to keep the source data resource stable before snapshot is executed, thus keeping consistency between the snapshot resource and the source data resource.
Step6 Click Finish to create the TimeMark.
To display the TimeMark policy and TimeMarks of a logical resource with TimeMark enabled, follow these steps:
Step1 Right-click the logical resource in the navigation tree and from the shortcut menu select Refresh to refresh the information about the logical resource.
Step2 Select the TimeMark tab in the content pane to display the TimeMark policy and TimeMark list of the logical resource as shown in Figure 12-3.
Figure 12-3 Display the TimeMark policy and TimeMarks of a logical resource
With the TimeMark copy feature of the IX3000, you can create an independent, permanent logical resource (target resource) from an existing TimeMark to get a full copy of data as it was at the time point corresponding to the TimeMark. This logical resource can be assigned to one or multiple SAN clients.
l The system does not support copying multiple TimeMarks at a time.
l Before creating a TimeMark copy, make sure that adequate space is available on the physical resource.
l Failover or recovery during a TimeMark copy process can cause copy failure and result in an invalid TimeMark copy. After the failover or recovery finishes, you need to manually delete the TimeMark copy and re-perform TimeMark copy.
To copy the TimeMark of a single SAN resource with TimeMark enabled, follow these steps:
Step1 Right-click the logical resource in the navigation tree and from the shortcut menu select the TimeMark > Copy. The TimeMark Copy Setup Wizard appears. Click Next.
Step2 In the wizard window shown in Figure 12-4, select the TimeMark to be copied from the list of TimeMarks and click Next.
Figure 12-4 Copy a TimeMark (1)
Step3 In the window shown in Figure 12-5, select a method to create a target resource for the TimeMark and click Next. (The methods of creating target resources for TimeMark copies are similar to those for snapshot copies. For details, refer to Chapter 11 “Snapshot and Snapshot Copy.”)
Figure 12-5 Copy a TimeMark (2)
Step4 In the window shown in Figure 12-6, assign a name to the target resource and click Next.
Figure 12-6 Copy a TimeMark (3)
Step5 Check that the settings you made are correct and click Finish to create the target resource for the TimeMark copy. After the TimeMark copy is completed, the target resource appears on the logical resource list.
You can select the General tab in the content pane of the logical resource to check the current status of the TimeMark copy.
The procedure of deleting a TimeMark copy is the same as that of deleting a SAN resource.
To modify the TimeMark properties of a SAN resource with TimeMark enabled, follow these steps:
Step1 Right-click the SAN resource in the navigation tree.
Step2 Select TimeMark > Properties from the shortcut menu. The TimeMark Properties dialog box appears, as shown in Figure 12-7.
Figure 12-7 Modify the TimeMark properties
Step3 Modify the TimeMark properties as required and click OK to confirm the operation.
Before disabling TimeMark on a logical resource, make sure that no TimeViews exist on the logical resource and no TimeMark copy is in process. If there are TimeViews, delete them first.
To disable TimeMark on a logical resource, follows these steps:
Step1 Right-click the logical resource in the navigation tree and from the shortcut menu select TimeMark > Disable.
Step2 In the confirmation dialog box that appears, type YES and click OK to disable TimeMark.
If CDP is enabled, the system disables CDP first when you attempt to disable TimeMark:
l If the CDP journal resource has data to submit, the system removes the CDP resource after all data is submitted. After that, you need to disable TimeMark manually.
l If the CDP journal resource has no data to submit, both TimeMark and CDP are disabled.
After you disable TimeMark, all the TimeMarks created for the logical resource are deleted, and the TimeMark tab in the content pane disappears.
l To delete a TimeMark, you need to delete the TimeView associated with it first.
l If the TimeMark deleted is the first TimeMark of a logical resource, the system releases the snapshot resource space used by it. If the TimeMark is not the first one, the system merges all the data of the TimeMark to the previous TimeMark and does not release the snapshot resource space.
To delete the TimeMark of a logical resource, follow these steps:
Step1 Right-click the logical resource in the navigation tree and from the shortcut menu select TimeMark > Delete. The Delete TimeMark dialog box appears, as shown in Figure 12-8.
Step2 Select the TimeMark to be deleted from the list of TimeMarks.
Press the Shift key to select multiple TimeMarks.
Step3 Click Delete. In the confirming dialog box, type YES and click OK. Then the system deletes the selected TimeMark. Check that the TimeMark disappears from the TimeMark tab.
This section takes configuring CDP for a SAN resource as an example. You can configure CDP for replica resources in a similar way.
When working with CDP, you can perform these tasks:
l Adding a Mirror for a CDP Journal
l TimeMarks are created based on the system time of the NeoStor server. To ensure the normal operation of CDP, which is based on TimeMarks, do not change the system time of the NeoStor server after the TimeMark function is enabled.
l Before enabling CDP for a logical resource, make sure that a snapshot resource has created for the logical resource.
l For replica resources, CDP takes effect only when they are created in continuous replication mode. Therefore, before enabling CDP for replica resources, make sure that the continuous replication mode is selected.
To enable CDP for a SAN resource, follow these steps:
Step1 Right-click the SAN resource in the navigation tree and from the shortcut menu select TimeMark > Enable.
Step2 In the window that appears as shown in Figure 12-9, select the Enable Continuous Data Protection option to enable CDP, and then click Next.
If the resource to be enabled with CDP has not been configured with a snapshot resource, you will be asked to configure one when enabling CDP. For how to create a snapshot resource, refer to Chapter 11 “Snapshot and Snapshot Copy.”
Step3 Select one or more physical devices where you want to create the CDP journal resource and click Next, as shown in Figure 12-10.
Figure 12-10 Select physical devices for the CDP journal resource
Step4 Select a method to allocate space to the CDP journal resource, Express for example, and click Next, as shown in Figure 12-11.
l The minimum CDP journal resource size is 1024 MB.
l If the Custom method is selected, you need to manually select physical resources for space assignment. If the Express method is selected, the system allocates space from available physical resources automatically. The method of creating a CDP journal resource is similar to creating SAN resources and snapshot copies.
Figure 12-11 Select a method to allocate space for the CDP journal resource
Step5 Configure the automatic CDP journal resource expansion policy, as shown in Figure 12-12.
Figure 12-12 Set the automatic CDP journal resource expansion policy
Table 12-1 describes how to configure the automatic CDP journal resource expansion policy.
Table 12-1 Configure the automatic CDP journal resource expansion policy
|
Field |
Action |
|
Automatically allocate more space for the CDP Journal |
Select or clear the option to enable or disable automatic CDP journal resource expansion. The option is selected by default and you are recommended to use the default. |
|
Continuous coverage period |
Set the CDP protection period, which ranges from 1 hour to 30 days.
Ensure that the CDP resource is large enough. When the CDP resource is unavailable or has no enough space, CDP cannot work normally to protect data. |
|
Journal expansion trigger |
Set a journal expansion triggering threshold. When the space used by the CDP resource reaches the threshold, expansion is triggered. |
|
Amount to allocate when triggered |
Set the expansion size, a percentage of the initial CDP journal resource. |
|
Maximum journal size |
Set the maximum size of the CDP journal resource. The value of 0 indicates that the CDP journal resource size is not limited. When the CDP journal resource size reaches the limit, the period protected by CDP may decrease. |
|
The Advanced button |
Click to set the performance level of updating the CDP journal resource in the window that appears as shown in Figure 12-13. Two options are available: l Moderate: Updates the CDP journal resource data depending on the system status. Adopt this option if write to the SAN resource is infrequent. l Aggressive: Updates the data on the CDP journal resource faster but may affect system performance. Adopt this option if write to the SAN resource is frequent. |
Figure 12-13 Set the performance level of updating the CDP journal resource
Step6 Set the TimeMark policy for the SAN resource in the window that appears as shown in Figure 12-14.
Figure 12-14 Set the TimeMark policy
Using TimeMark, you can restore data to a specific point in time. Using TimeMark in conjunction with CDP, you can restore data to any point in a certain protected period.
Table 12-2 describes how to set a TimeMark policy.
Table 12-2 Set a TimeMark policy
|
Field |
Action |
|
Create an initial TimeMark on… |
Set the time at which the initial TimeMark is to be created and the interval for creating subsequent TimeMarks.
l Normally you must set an initial TimeMark creation time. If you fail to do that, no TimeMark will be created even if TimeMark is enabled. For a replicated-in resource, however, you do not need to do that, because a TimeMark is created automatically each time after a replication is performed. l The interval for creating TimeMarks can be any value in the range of 10 minutes to 1 day. l Because the initial TimeMark is created based on the system time of the console PC while subsequent TimeMarks are created based on the system time of the NeoStor server, make sure that the system time settings of the console PC and the NeoStor servers are synchronized to avoid anomalies. |
|
Maximum Number of TimeMarks to Keep |
Set the maximum number of TimeMarks to be retained. For how to set this option, refer to the note below this table. |
|
Trigger snapshot notification… |
Set the snapshot notification interval.
Snapshot notification collaborates with snapshot proxy to notify SAN clients of coming snapshots. The user will then be prompted not to perform any operation that may change the status of data on disk, thus ensuring integrity of snapshot data. As snapshot notification requires acknowledgement, snapshot performance may be affected when a SAN client is busy. To ensure snapshot performance, you can choose to clear the snapshot notification option if you are sure that the SAN client will not update data when snapshot is being performed. |
l The maximum number of TimeMarks that CDP requires depends on the period that CDP covers and the interval for creating TimeMarks. For example, if you set the coverage period is set to 30 days, and the TimeMark creating interval to 1 hour (that is, creating 24 TimeMarks per day), the total number of required TimeMarks is 720 (24 × 30). The system, however, can retain only 255 at maximum. When this limit is reached, TimeMarks will be deleted resulting in loss of data at the corresponding points in time. If the maximum number of TimeMarks to keep is set exceeding 255, the system will display a warning message asking you to re-adjust the setting, as shown in Figure 12-15.
l The minimum number of TimeMarks required for continuous protection equals continuous coverage period / TimeMark creating interval + 1. For example, if the continuous coverage period is 24 hours, and the TimeMark creating interval is 1 hour, then the minimum number of TimeMarks needed is 25 (24/1 + 1).
Figure 12-15 Message asking for CDP setting adjustment
Step7 In the window shown in Figure 12-16, check that the settings you made are correct and click Finish to complete the operation of enabling CDP. A CDP tab then appears in the content pane of the SAN resource.
Figure 12-16 Confirm the CDP settings
To check the CDP information of a SAN resource, select the CDP tab in the content pane of the SAN resource. The tab displays CDP information such as the CDP journal resource size and the CDP expansion policy, as shown in Figure 12-17.
Figure 12-17 Check CDP information
A TimeMark created for a CDP journal is displayed on the TimeMark tab only after the data in the journal at the corresponding point in time is flushed to the SAN resource. When a write to the SAN resource involves a large amount of data, the display of the TimeMark on the TimeMark tab may be deferred because of the flushing delay.
You can protect a CDP journal by using the mirroring function.
To add a mirror for the CDP journal of a SAN resource, follow these steps:
Step1 Right-click the SAN resource in the navigation tree.
Step2 Select TimeMark > CDP Journal > Mirror > Add from the shortcut menu to add a mirror for the CDP journal resource.
To identify CDP journal resources conveniently, you can tag each CDP journal resource with certain information.
You are recommended to use only English letters and digits for CDP journal tags.
To tag the CDP journal of a SAN resource, follow these steps:
Step1 Right-click the SAN resource.
Step2 Select TimeMark > CDP Journal > Add a Tag from the shortcut menu. The dialog box shown in Figure 12-18 appears.
Figure 12-18 Add a CDP journal tag
Step3 Input a descriptive string for the CDP journal and click OK.
To modify the CDP policy of a SAN resource, follow these steps:
Step1 Right-click the SAN resource in the navigation tree.
Step2 Select TimeMark > Properties from the shortcut menu. The TimeMark Properties dialog box appears, as shown in Figure 12-19.
Figure 12-19 Modify a CDP policy
Table 12-3 describes the tabs in the window shown in Figure 12-19. For how to set the parameters on each tab, refer to Enabling CDP.
Table 12-3 Description on the tabs
|
Tab |
Description |
|
TimeMark Schedule |
Modify the TimeMark policy |
|
CDP Option |
Disable CDP |
|
CDP Journal |
Modify the CDP policy |
Step3 Modify the CDP properties as required and then click OK to commit the settings.
After enabling mirroring or replication for a CDP-enabled resource, you can suspend CDP to avoid system resource conflict. If the resource is in a group, you need to suspend CDP for the whole group.
Suspending CDP does not remove any CDP resource or TimeMark.
To suspend CDP for a SAN resource, follow these steps:
Step1 Right-click the SAN resource or the resource group to which the SAN resource belongs.
Step2 Select TimeMark > CDP Journal > Suspend from the shortcut menu to suspend CDP. On the CDP tab in the content pane, you can see that the status of CDP changes to suspended.
To resume suspended CDP for a SAN resource, follow these steps:
Step1 Right-click the SAN resource or resource group to which the SAN resource belongs.
Step2 Select TimeMark > CDP Journal > Resume from the shortcut menu to resume CDP. On the CDP tab in the content pane, you can see that the status of CDP changes to suspended.
After CDP is resumed, the system can continue to write data to the CDP journal.
You can disable CDP by disabling TimeMark (refer to Disabling TimeMark) or disable CDP without disabling TimeMark.
This section is focused on the latter.
To disable CDP without disabling TimeMark for a SAN resource, follow these steps:
Step1 Right-click the SAN resource in the navigation tree and from the shortcut menu select TimeMark > Properties.
Step2 In the TimeMark Properties window that appears, select the CDP Option tab and unselect the Enable Continuous Data Protection option.
Step3 In the confirmation dialog box that appears, type YES and click OK to disable CDP.
As a result, the CDP tab disappears.
When working with TimeView, you can perform these tasks:
l Restoring Data with TimeView
l Assigning a TimeView to Clients
l Rolling Back a Logical Resource
TimeView can mount the virtual image as of a specific time point. SAN clients can access the image data like accessing a local HDD.
To restore data with TimeView for a logical resource, follow these steps:
Step1 Right-click the resource and from the shortcut menu select TimeMark > TimeView. The dialog box shown in Figure 12-20 appears.
Figure 12-20 Create a TimeView
Step2 Select to create TimeViews from the CDP journal or TimeMark snapshots. Two options are available:
l Select the Create TimeView from the Continuous Data Protection Journal option.
Table 12-4 shows how to select a time point from the CDP journal.
Table 12-4 Select a time point from the CDP journal
|
Method |
Action |
|
Drag the sliding bar |
Drag the sliding bar of the bar graph to the specific time point. The bar graph is described as follows: l As shown in Figure 12-20, a bar graph is used to indicate the TimeMark status in the Select Data Point area. Each bar represents a TimeMark. The Y axis shows the data condition of a TimeMark, that is, the height of each bar shows the space used by the corresponding TimeMark; the X axis shows the time. A TimeMark can be illustrated in the graph only when it has data. l The bar graph reflects data change. Greater data changes can be reflected more clearly in the bar graph. Comparatively, if the data keeps stable, the bar graph cannot reflect the differences between TimeMarks. |
|
Input the time |
Configure the specific time point settings for creating the TimeView in the text boxes under the bar graph. In the two spin boxes, you can fine tune the time in milliseconds and microseconds.
You can select an approximate time by dragging the sliding bar and then manually fine tune the time in the text boxes. |
|
Use the Zoom In button |
Click the Zoom In button to view detailed data I/O information as of the point in time in a specific time range (see Figure 12-21). By examining data I/O in a certain time range, you can select an appropriate recovery point in time. |
|
Use the Select Tag button |
Click Select Tag to select a CDP journal tag to restore data as of the point in time corresponding to the tag. See Figure 12-23. |
You are recommended to select a time point where no data I/O is performed for data recovery.
Figure 12-21 View I/O as of a point in time
Table 12-5 describes how to use the buttons and sliding bar in the window shown in Figure 12-21 to view I/O as of a point in time.
Table 12-5 View I/O as of a point in time
|
Element |
Action |
|
The forward and backward buttons ( |
If no data is displayed when you open the window shown in Figure 12-21, click the forward or backward icon at the bottom to scroll data display forwards or backwards by five minutes. |
|
Sliding bar |
Drag the sliding bar to view I/O state as of a point in time in a time range. |
|
The Zoom In button |
Click to view detailed I/O data as of the point in time selected with the sliding bar. See Figure 12-21. |
|
The Zoom Out button |
Quit the Zoom In view. |
|
The Search button |
Click to display I/O data in smaller time units. See Figure 12-22. |
Figure 12-22 Search the CDP journal
Table 12-6 describes how to use the CDP journal search criteria in the Search CDP Journal window shown in Figure 12-22.
Table 12-6 Set the CDP journal search criteria
|
Field |
Action |
|
Quiescence Point |
Select to set the time unit in which I/O data is displayed. After you set the time unit in the Minimum Time field, you can click OK repeatedly to display I/O data in the time unit over the time range selected by the sliding bar in the window shown in Figure 12-21. |
|
Data Point |
Select to search for points in time where the number of I/Os per second equals the value set in the Minimum I/O’s box. As shown in Figure 12-20, the time points with one I/O per second are displayed. |
Figure 12-23 Select a time point based on CDP journal tag
l Select the Create TimeView from TimeMark Snapshots option to restore data from TimeMark snapshots. In the window shown in Figure 12-20, select the desired TimeMark from the TimeMark list, and then click OK.
Step3 After selecting a specific time point, click OK to create a TimeView for it.
Step4 Input a name for the TimeView, and click OK, as shown in Figure 12-24.
Figure 12-24 Name the TimeView
Step5 Assign the TimeView to clients. (For how to assign a TimeView to a client, refer to Chapter 9 “SAN Clients.”) After you assign the TimeView to a client, the client can restore data from the TimeView.
A TimeView is not accessible when failover is being performed. After the failover task is finished, it becomes accessible.
To map a TimeView created from a TimeMark to another TimeMark, perform the TimeView remapping operation.
l TimeView remapping is available only for TimeViews of SAN resources.
l If a TimeView has been assigned to a SAN client, you need to disconnect it from the client before remapping it and re-connect it to the client after remapping. Otherwise, the data in the TimeView cannot be flushed to the virtual drive mounted from the TimeView on the SAN client.
To remap a TimeView, created from TimeMark A for example, follow these steps:
Step1 Under the SAN Resources node in the navigation tree, right-click the TimeView resource created from TimeMark A and from the shortcut menu select Remap.
Make sure that the TimeMark you want to remap the TimeView to has been created.
Step2 Select the TimeMark you want to remap the TimeView to, TimeMark B for example, from the list of existing TimeMarks, and click Next.
Step3 Input a new name for the TimeView and click Finish to complete TimeView remapping. As a result, the TimeView created from TimeMark A is remapped to TimeMark B.
By assigning a TimeView to the target of a SAN client, you can enable the SAN client to access the TimeView.
l You can assign a TimeView to multiple targets.
l You cannot assign a TimeView to two or two more targets of the same client.
Assigning a TimeView to SAN clients is similar to assigning a SAN resource to SAN clients. For details, refer to Chapter 8 “Logical Resources.”
Renaming a TimeView is similar to renaming a SAN resource. For details, refer to Chapter 8 “Logical Resources.”
l After you rename a TimeView that has been assigned to SAN clients, the TimeView under these clients refreshes its name automatically.
l You can rename a TimeView when snapshot copy is being performed. This is because a snapshot copy is identified by a virtual ID; so long as the virtual ID keeps the same, the snapshot copy process can be performed normally.
The IX3000 supports rolling a logical resource back to a specific point in time (time point A for example) based on the TimeMarks or CDP journal of the logical resource. After rollback, the logical resource is the same as it was at time point A.
The following uses an example to show the difference between TimeMark-based rollback and CDP journal-based rollback.
A TimeMark is created at time A and later at time B for a logical resource. When detecting a data error, roll back the logical resource to TimeMark A. If TimeMark-based rollback is performed, all TimeMarks later than TimeMark A will be lost and cannot be recovered. If CDP journal-based rollback is performed, the TimeMarks (including TimeMark B) after TimeMark A can still be recovered.
l Before rolling back a SAN resource, disconnect all SAN clients from it and unassign the resource. For how to unassign a SAN resource, refer to Chapter 8 “Logical Resources.”
l To avoid anomalies, make sure that no TimeViews are created from any TimeMark later than the TimeMark you want to roll back to.
l How long a rollback lasts depends on delta data. You need to make sure that the data is rolled back completely before performing any other operations on the SAN resource.
To roll back a logical resource with TimeMark/CDP enabled to a TimeMark, follows these steps:
Step1 Right-click the logical resource in the navigation tree and from the shortcut menu select TimeMark > Rollback. A dialog box appears.
Step2 Select the time point to which you want to roll back from the list of TimeMarks or the CDP journal resource and click OK.
Step3 In the confirmation dialog box, type YES and click OK. The system starts the rollback operation.
Step4 Select the General tab in the content pane of the logical resource to verify that the logical resource has been rolled back to the TimeMark.
To enable the logical resource to be accessible to a SAN client, you must re-assign the logical resource after the rollback is completed.
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