What is a consistency check?
Published : April 8, 2005 | Updated : August 17, 2005
Data Protection Manager (DPM) provides two methods for synchronizing a replica: incremental synchronization and synchronization with consistency check. Synchronization with consistency check, also referred to as “a consistency check,” is the process by which DPM checks for and corrects inconsistencies between a protected volume and its replica. As part of the synchronization process, a consistency check performs block-by-block verification to ensure that all the data on the replica is consistent with the protected data. This process is slower than incremental synchronization because all the data on the replica is compared rather than just applying the data changes to the replica.
DPM automatically performs a consistency check in the following instances:
When a replica is created for a new protection group
When you protect new data sources by adding them to an existing protection group
As a daily task, if you have scheduled a daily consistency check for a protection group
If a replica becomes inconsistent because of a synchronization log overflow or an unexpected shutdown of the file server, a consistency check must be performed. You can perform a one-time manual consistency check or, if a daily consistency check is scheduled, you can wait until DPM performs a consistency check. When a consistency check is performed and inconsistencies between the protected volume and the replica volume are found, DPM makes the replica consistent.
Note
The performance of the file server and the DPM server will be affected while a consistency check is running. It is best to schedule consistency checks and perform one-time consistency checks during off-peak hours.