Sql server differential backups vary in size

Question

I set up a SQL Server maintenance plan as follows:

• Full backup every Sunday at 2am
• Differential backup every 3 hours

After a full backup was made, I noticed that differential backups vary in size. At first he started small and grew accordingly. However, at different points, some differential backup files may be larger or smaller than before. This includes large differences (for example, from 200 MB to 3 MB). I know that no other full backups were performed, and at that time a large amount of data was not deleted. What would be the reason, and is there something I am missing? Based on my research, the differential should do nothing but increase until another full backup is taken.

Any insight would be appreciated.

Thank!

Answer 1

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Edit

. Microsoft ( ), READ_WRITE_FILEGROUPS. AFAIK, T-SQL, :

BACKUP DATABASE [SampleDB] READ_WRITE_FILEGROUPS
TO DISK = N'C:\SQLBackups\SampleDB_PARTIAL_Diff.bak'
WITH DIFFERENTIAL
GO