About file and filegroup backups
SQL Server also supports the backup of up individual filegroups and files as distinct images. A filegroup is composed of one or more database files. A backup of the constituent files of a filegroup is logically equivalent to a backup of the filegroup itself.
Filegroup and file backups would commonly be used in a tightly architected application in which physical disk locations were mapped to logical objects. For example, tables and indexes.
The following factors may lead you to use file and filegroup backups in this type of environment:
Some portions of the database should be backed up more frequently than other portions, especially those that may be volatile or mission critical.
The database may be so large that the time that is required for a full database backup cannot fit in the allocated time window. Thus it may be more viable to do a full backup of one or more files or filegroups on a rotating basis.
You may want to optimize on backup volume and recovery speed by placing some of your data into read-only filegroups.
In the event of disk failure, you can choose to recover only the failed unit from a filegroup backup or file backup. You do not have to restore the entire database.
To use filegroup and file backups you must maintain backups of the transaction log.
For example, to perform a full database restore using filegroups and files, you are required to restore the following:
All of the constituent filegroups and files
All of the transaction log segments
These translation logs segments must start from the first component backup until a point in time following the last component backup.
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