Maximum Fragment Size

The Maximum Fragment Size setting specifies (in megabytes) the largest fragment size that NetBackup can create when storing backups.

Another benefit of fragmenting backups on disk is increased performance when restoring from images that were migrated by Storage Migrator. For example, if a 500 megabyte backup is stored in 100 megabyte fragments, you can restore a file quicker because Storage Migrator has to retrieve only the specific fragment with the file rather than the entire 500 megabytes.

For Media Manager storage units:

The default maximum fragment size for a Media Manager storage unit is 1 terabyte. To specify a maximum fragment size other than the default, place a check in the Maximum Fragment Size check box, then enter a value of 50 megabytes to 1048576 megabytes (1 terabyte).

Fragmenting tape backups can speed up restores by allowing NetBackup to skip to the specific fragment before searching for a file. Otherwise, NetBackup starts at the beginning of the backup and reads tar headers until finding the desired file.

For hard disk storage units:

The default maximum fragment size for a disk storage unit is 2000 megabytes. To specify a maximum fragment size other than the default, enter a value that ranges from 20 megabytes to 2000 megabytes.

Fragmenting disk backups is normally used to ensure that the backup does not exceed the maximum size allowed by the file system. It is intended primarily for storing large backup images on a disk type storage unit. Another benefit of fragmenting backups on disk is increased performance when restoring from images that were migrated by Storage Migrator. For example, if a 500 megabyte backup is stored in 100 megabyte fragments, you can restore a file quicker because Storage Migrator has to retrieve only the specific fragment with the file rather than the entire 500 megabytes.

If an error occurs in a backup, the entire backup is discarded and the backup restarts from the beginning, not from the fragment where the error occurred.