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Recovery Goals for Disk-Based Protection

更新日期: 2010年4月

適用於: System Center Data Protection Manager 2010

Although all members of a protection group share the same synchronization frequency, the synchronization process and the resulting recovery point schedule differ based on the type of data being protected. For more information, see How DPM Works.

Synchronization and Recovery Points for Files

For a file volume or share, the protection agent on the protected computer tracks changed blocks in the change journal that is part of the operating system. During synchronization, these changes are transferred to the DPM server and then applied to the replica to synchronize the replica with the data source.

You can select a synchronization frequency interval of anywhere from 15 minutes to 24 hours. The default is 15 minutes. You can also select to synchronize only before a recovery point is created.

Recovery points, which are shadow copies of the replica for file data, are created from the synchronized replica on a configurable schedule. Each file synchronization does not result in a recovery point unless you synchronize only before each recovery point; however, you can manually create a recovery point from the most recent file synchronization.

For example, a volume is synchronized hourly and a recovery point for the volume is created at 8:00 A.M., 12:00 P.M., and 6 P.M. A user makes changes to a file on the volume at 1:30 P.M.; however, when another user makes changes an hour later, the file is inadvertently corrupted, and you are asked to recover the file with the first user's changes. Because the changes at 1:30 P.M. were made after the most recent recovery point was created at 12:00 P.M., you cannot recover the file from the most recent recovery point. However, you can manually create a recovery point from the appropriate synchronization of that replica and then recover the file from that new recovery point.

The default schedule creates recovery points at 8:00 A.M., 12:00 P.M., and 6:00 P.M. daily. You can modify both the times and the specific days. You cannot specify different times for different days. For example, you can schedule recovery points for 2:00 A.M. and 2:00 P.M. on weekdays only; however, you cannot schedule recovery points for 2:00 A.M. on weekdays and at 12:00 P.M. on weekends.

Retention Range for Files

Retention range is the duration of time for which the data should be available for recovery. When the retention range for a recovery point expires, the recovery point is deleted.

You can select a retention range between 1 and 448 days for short-term disk-based protection, up to 12 weeks for short-term tape-based protection, and up to 99 years for long-term tape-based protection. DPM can store a maximum of 64 recovery points for each file member of a protection group.

For example, if you select to synchronize before each recovery point and you schedule 6 recovery points daily, and you set a retention range of 10 days, recovery points for the files in that protection group never exceed 64. However, if you choose a combination of settings that exceeds the limit of 64 recovery points, DPM warns you during the configuration process so that you can modify your selections; you cannot configure a protection configuration for files that exceeds the limit of 64 recovery points.

Synchronization and Recovery Points for Application Data

For application data, changes to volume blocks belonging to application files are tracked by the volume filter. Synchronization of application data is analogous to an incremental backup and creates an accurate reflection of the application data when combined with the replica.

You can select a synchronization frequency interval of anywhere from 15 minutes to 24 hours. The default is 15 minutes. You can also select to synchronize only before a recovery point is created. If you select to synchronize only before a recovery point is created, DPM performs express full backup to synchronize the replica according to the recovery point schedule.

For applications that support incremental backups, the default schedule results in recovery points for each synchronization (every 15 minutes) and for the express full backup at 8:00 P.M. daily. For applications that do not support incremental backups, the default schedule results in a recovery point for the express full backup at 8:00 P.M. daily.

You can modify both the times and the specific days. You cannot specify different times for different days. For example, you can schedule recovery points for 2 A.M. and 2 P.M. on weekdays only; however, you cannot schedule recovery points for 2 A.M. on weekdays and at 12:00 P.M. on weekends.

Exception for Some SQL Server Databases

Transaction log backups, which DPM uses for incremental synchronization of application data, cannot be performed for a SQL Server database that is read-only, configured for log shipping, or configured to use the Simple Recovery Model. For those SQL Server databases, recovery points correspond to each express full backup.

Comparing Synchronization and Express Full Backup

To enable faster recovery time, DPM will regularly perform an express full backup in place of incremental synchronization. An express full backup is a type of synchronization that updates the replica to include the changed blocks.

note附註
You can modify the express full backup schedule for any protection group that contains application data by using the Optimize performance action in the Protection task area or by using the Modify Group Wizard.

Retention Range for Application Data

You can select a retention range between 1 and 448 days for short-term disk-based protection, up to 12 weeks for short-term tape-based protection, and up to 99 years for long-term tape-based protection.

For example, if you select to synchronize every 15 minutes and you set a retention range of 10 days, those recovery goals result in a protection plan that maintains 960 recovery points for application data in that protection group after the initial 10 days of data protection.

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