Veritas NetBackup™ Deduplication Guide

About MSDP storage rebasing

During an initial backup, NetBackup writes the data segments from a backup to as few container files as possible. Read performance is best when the data segments from a client backup are close to each other on deduplication storage. NetBackup consumes less time finding and reassembling backed up files when their segments are near each other.

However, the data segments in a backup may become scattered across the disk storage each time the client is backed up. Such scattering is a normal consequence of deduplication.

NetBackup includes a process, called rebasing, that helps to maintain the data segments in as few container files as possible. Rebasing improves performance for the operations that read from the storage, such as restores and duplications. NetBackup writes all of the data segments from a backup into new container files even though the segments exist on storage already. Future backups then refer to the new copies of those segments rather than the old copies until any changes because of future rebasing. Deduplication rates for the backup jobs that perform rebasing are lower than for the jobs that do not rebase the data.

After the rebasing, NetBackup reclaims the storage space that the rebased data segments used.

Table: Types of rebasing describes the rebasing operations.