Summary

This Knowledgebase article provides information about how to configure Neverfail Continuity Engine to create shadow copies and configuration options for the Neverfail Engine Data Rollback Module.

More Information

Neverfail Engine provides the ability to configure automatic creation of shadow copies via the Data Rollback module Configuration pane.  To learn more about configuring automatic shadow copy creation, follow the procedures below.

Procedure

How to Configure Neverfail Engine to Create Shadow Copies Automatically

To create shadow copies automatically, follow the steps below:

1. Launch the Neverfail Advanced Client and select the Data: Rollback tab and clic the Configuration button.
2. Select the frequency and time periods for creating shadow copies.
3. Select which shadows will be kept, and which removed for earlier time periods.
   
   The Data Rollback Module provides a flexible method of scheduling the creation of new shadow copies and deleting older shadow copies. You should configure the schedule to match your clients' working patterns, the required granularity of data-restoration, and the available storage. For example, do clients tend to work 9am-5pm, Monday-Friday in a single time zone, or throughout the day a cross multiple time zones?  You should avoid taking shadow copies during application maintenance periods, such as Exchange defragmentation, or a nightly backup. In determining how frequently to create new shadow copies, and when to discard older ones, you must balance the needs for fine-granularity of restorable points-in-time versus available disk space, and the upper limit of 512 shadow copies across all shadowed volumes on the server.
   Most shadow copies will be taken on a passive server, but you may select to create one shadow copy per day on the active server. This will be accomplished with the cooperation of the application for VSS-aware applications, such as Exchange and SQL Server.  As this may cause a temporary suspension of application activity, it is recommended to schedule this for periods system loads are light.
   
   Please note that when the Data Rollback Module is configured to create and manage shadow copies automatically, this task will run at the selected frequency (for example, every 15 minutes) and will be reflected in the status display, which indicates when the task will next run.  The task will not necessarily create a shadow every time it runs, as this is determined by the configuration of the schedule.

The timestamp associated with a shadow copy refers to the system time of the server on which the shadow copy is taken.

How to Configure the Schedule

The Data Rollback Module can create and delete shadow copies automatically according to a configurable schedule. The intent of the schedule is to provide a balance between providing a fine granularity of rollback points-in-time on the one hand, and conserving disk space and the number of shadow copies on the other. In order to achieve this balance, the available configuration options make use of the belief that recent events tend to be of more interest than more distant ones. Therefore, the default schedule will maintain one shadow from every day of the last week, and one shadow from every week of the last month.

The following configurable options are available from the Data: Rollback -> Configure Shadow Schedule dialog:

Create and maintain shadows automatically - This check box determines if shadow copies are to be automatically created and deleted.  If selected, shadow copies will be automatically created and deleted in line with other user configuration settings. When this check box is cleared, you can still manually create/delete and rollback shadow copies from the Status & Control panel.

Note: The Shadow Copy Service component of Windows Server, may automatically delete old shadow copies because of lack of disk space, even when the Create and maintain shadows automatically check box is cleared.

Shadow Creation Configuration Options

These options set the frequency for shadow creation on the passive and active server respectively.

Note: No shadows will be created when the system is 'Out-Of-Synch' or 'Not Replicating'.

• Create a shadow every: - This drop down list controls how frequently a shadow copy is taken. The default setting is every 30 minutes.  When a shadow copy is actually taken it is also controlled by Only between the hours: and Only on the days : . If either of these are set, then shadow copies are taken at the frequency defined by this drop down list, but only within the days/hours defined by them.

• Create a shadow on the Active once per day at: - If the check box is cleared, then no shadows will be automatically created on the active server. If it is selected, then a shadow copy will be taken each day at the time selected from the drop down list.  The shadow copy will be taken with "Application cooperation”, which means that if the Application protected by Neverfail Engine is integrated with VSS, it will be informed before the shadow is taken and given the opportunity to perform whatever clean-up it is designed to do when a VSS shadow copy is taken.

Whether a shadow copy is actually taken, is also controlled by Only between the hours: and Only on the days: . If either of these are set, then a shadow copy will only be taken within the days/hours defined by them.

Warning: it is possible to select a time that is not within the Only between the hours: range, this will result in the shadow not being created.

These two options limit the number of shadows taken when the system is not very active in order to avoid creating shadows when the data is not changing:

• Only between the hours: checkbox, start time drop down list, and end time drop down list. If the check box is selected, then the range defined by the two drop down lists will be applied to the automatic creation of shadow copies either on the passive server or active server (as controlled by Create a shadow every: and Create a shadow on the Active once per day at: respectively).

Note: It is possible to define a range of 20:00 to 06:00 when shadow copies are to be only taken at night.

• Only between the days: checkbox, start day drop down list and end day drop down list. If the check box is selected, then the range defined by the two drop down lists will be applied to the automatic creation of shadows either on a passive or the active server (as controlled by Create a shadow every: and Create a shadow on the Active once per day at: respectively).

Note: It is possible to define a range of Saturday to Sunday when shadow copies are to be only taken during weekends.

Shadow Copy Creation Keep Options

The purpose of the following three options is to “thin-out” older shadow copies while preserving a series, which spans the previous 35 days.

Note: Manually created shadow copies will not be deleted automatically, however VSS will delete old shadow copies (whether manually created or not) whenever it requires additional disk space for the creation of a new shadow copy.  When manually created shadow copies match the criteria for keeping a shadow from a particular time period, then automatic shadow copies in close proximity will be deleted.  For example, a manually created shadow will not be deleted, but can be used for the “keep algorithm”.

• For earlier in the current day keep shadows only at an interval of: check box and drop down list. If the checkbox is selected, then only the first shadow copy will be kept for each interval.  “Earlier in the current day” means since Midnight and older than an hour.  The intervals will be calculated from either at Midnight or if Only between the hours: is checked, then from the start hour. For shadow copies taken before the start time (as it may have changed), the interval is calculated backwards again starting at the start time.
• For earlier days in the current week, keep only the shadow nearest: check box and drop down list. If the check box is selected, then only the shadow copy nearest the selected time will be kept for each day.  Earlier days in the current week means the previous seven days not including today (as today is covered by the above option). Each day means Midnight to Midnight.
  
  Note: If a shadow copy was taken at 5 minutes to midnight on the previous day, it will not be considered when calculating the nearest.
• For earlier weeks in the current month, keep only the shadows nearest: check box and drop down list. If the check box is selected, then only the shadow copy nearest to the selected day will be kept for each week.  “Earlier weeks in the current month” means the previous four weeks not including either today or the previous 7 days (as they are covered by the above two options).

Note: In order to calculate the “nearest”, an hour is required. The calculation will attempt to use the selected time from For earlier days in the current week, keep only the shadow nearest: if it is selected, otherwise the Only between the hours: start time will be used if it is selected. Finally, when neither of these options are configured, Midnight will be used. All automatic shadow copies taken more than 35 days ago will be deleted.   The intervening 35 days are covered by the above three options

Applies To

Neverfail Continuity Engine

Related Information

None

KBID-2842