SQL Server Backup and Restore - Simple Talk

Chapter 9: File and Filegroup Backup and Restore
Hopefully, as discussed in the previous sections, this database has been architected such
that the data is spread across multiple data files, in several filegroups, so that we can still
back up the whole database bit by bit, by taking a series of file backups, scheduled on
separate days. While this is the most common reason for file backups, there are other
valid reasons too, as we have discussed; for example if one filegroup is read-only, or
modified very rarely, while another holds big tables, subject to frequent modifications,
then the latter may be on a different and more frequent backup schedule.
A file backup is simply a backup of a single data file, subset of data files or an entire
filegroup. Each of the file backups contains only the data from the files or filegroups that
we have chosen to be included in that particular backup file. The combination of all of
the file backups, along with all log backups taken over the same period of time, is the
equivalent of a full database backup. Depending on the size of the database, the number
of files, and the backup schedule, this can constitute quite a large number of backups.
We can capture both full file backups, capturing the entire contents of the designated
file or filegroup, and differential file backups, capturing only the pages in that file or
filegroup that have been modified since the last full file backup (there are also partial and
partial differential file backups, but we'll get to those in Chapter 10).
Is there a difference between file and filegroup backups?
The short answer is no. When we take a filegroup backup we are simply specifying that the backup file
should contain all of the data files in that filegroup. It is no different than if we took a file backup and
explicitly referenced each data file in that group. They are the exact same backup and have no differences.
This is why you may hear the term file backup used instead of filegroup backup. We will use the term file
backup for the rest of this chapter.
Of course, the effectiveness of file backups depends on these large databases being
designed so that there is, as best as can be achieved, a distribution of data across the data
files and filegroups such that the file backups are manageable and can complete in the
required time frame. For example, if we have a database of 900 GB, split across three
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