The minimum change journal size maintained by the Unitrends’ agent is 500MB. The file is located on the Windows client in the \PCBP directory (typically C:\PCBP). If use of the change journal is not desired, it can be disabled by modifying the following entry in the agent’s master.ini file. In this case, the agent includes some information in the backup output to warn the user that a new master backup must be completed in order to use the journal for subsequent incremental backups. If one of these checks fails, the agent does not use the journal and reverts to the volume scanning method. If both these checks succeed, then the agent uses the change journal to determine which files to include in the backup. In this case, there will be file modifications that were made to the volume that are not recorded in the journal. If these numbers do no match, this indicates that the journal was filled to capacity with entries and has ‘wrapped’ around to the beginning. If the IDs do not match, this indicates that the journal that existed during the master backup was deleted and that a new journal was created.Ī check to determine if the starting sequence number in the registry matches that of the volume’s current journal. Ī check to determine if the journal ID in the registry matches the ID of the volume’s current journal.If the entries exist, then the agent performs the following checks: This information will have been entered there by a previous master backup. If a journal exists, the agent queries the registry for the journal’s ID and starting sequence number. When an incremental backup is performed, the system is scanned for an existing change journal on each volume that it intends to back up. If the journal cannot be used, the agent uses the volume-scanning method to produce the list of files to back up. By default, the agent prefers to use the change journal during incremental backups. There are no visible configuration or setting options on the backup system or on Unitrends local agent interface. The change journal feature is transparent. As the number of files on a volume increases, the benefit of using the change journal also increases. Since journal records are kept only for changes to files or directories, determining which files to back up on a volume requires just a fraction of the time needed for the traditional volume scan. This is done by comparing the modified data to the time of the last successful master backup. It queries the data logged for each change to determine if the time of the change qualifies the data for back up. Windows logs all file changes on a given volume along with the nature and time of the change.ĭuring an incremental backup, the Unitrends agent queries the change journal to discover the changes made to files on the volume. When a change journal is created, Windows begins to log changes immediately to that journal without requiring a reboot of the server. The change journal is a record of all changes to any file(s) on a given volume. Use of the change journal can eliminate much of the overhead contributed by these factors. Additionally, files with the archive property set should not automatically be included in incremental backups. In addition, Factor 2 helps to inflate the size of the backup by including files that do not meet the modification criteria. If the property is set, then the file is included in the backup.įactor 1 accounts for a large percentage of the time spent performing the backup, while Factor 2 contributes more processing overhead from the mechanics of examining the file properties. Files with modification times more recent than the last successful master are included in the incremental backup.įactor 2 – The Windows agent also looks at the ‘archive’ property on each file whose modification time does not meet the first criteria. įactor 1 – The Windows agent scans all files/directories on the specified volumes to determine modification times.Two factors contributing to the delayed backup times include: Today, customers with large numbers of files (typically in the millions) can experience very long incremental backup times. You are here: Advanced Configuration Options > About the NTFS change journal About the Windows NTFS change journal
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