A SQL Server backup that captures only the data pages that have changed since the last full backup, but is limited to specific filegroups rather than the entire database.
- A differential backup captures all changes since the last full backup, while a partial differential backup applies this concept to selected filegroups: This approach is especially useful for very large databases (VLDBs).
- Partial backups and partial differential backups allow DBAs to back up read-write filegroups more frequently: Read-only filegroups can be backed up less often, helping reduce backup windows and storage requirements.
- This strategy is commonly used in data warehousing environments: Historical data filegroups are often configured as read-only, while only the current-period filegroup continues to receive updates.
- Restore sequences involving partial differential backups are more complex: DBAs should carefully plan and regularly test the complete restore process before depending on this strategy in production environments.
- Related terms: Differential Backup, Full Backup, Filegroup, Restore, VLDB.
