Using the VxFS file change log for incremental backups property

The Use VxFS file change log feature is supported on all platforms and versions where VxFS file systems support FCL.

The following VxFS file systems support FCL:

The File Change Log (FCL) tracks changes to files and directories in a file system. Changes can include files created, links and unlinks, files renamed, data that is appended, data that is overwritten, data that is truncated, extended attribute modifications, holes punched, and file property updates.

NetBackup can use the FCL to determine which files to select for incremental backups, which can potentially save unnecessary file system processing time. The FCL information that is stored on each client includes the backup type, the FCL offset, and the timestamp for each backup.

The advantages of this property depend largely on the number of file system changes relative to the file system size. The performance impact of incremental backups ranges from many times faster or slower, depending on file system size and use patterns.

For example, enable this property for a client on a very large file system that experiences relatively few changes. The incremental backups for the client may complete sooner since the policy needs to read only the FCL to determine what needs to be backed up on the client.

If a file experiences many changes or multiple changes to many files, the time saving benefit may not be as great.

See About the Backup Selections tab.

The following items must be in place for the Use VxFS file change log feature to work:

If the policy has Collect true image restore information or Collect true image restore information with move detection enabled, it ignores the Use VxFS file change log property on the client.

Additional information about the VxFS file change log feature: