Running out of disk space mid-restore
I have not tested it, but I would think the filestream file should be included in the size.


  For example, you can use all backup and recovery models with FILESTREAM data, and the FILESTREAM data is backed up with the structured data in the database.


Source

In addition, it sounds like you have emtpy pages.


  Note that the backup size does not include empty pages, but when you actually perform the restore, the data and log files will be over 200 GB, because it has to restore exactly what the source system had (including a 200+ GB log file, regardless of how full it was). 


Your example may not be 200+GB, but it was in the case for this person when their backup was pretty small.

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