[ 1 ], [ 2 ] and many other references gives conclusion that BLOBs with size less tha 0.3-1 MB should be stored in database while BLOBs larger than 1 MB – in file system (possibly through FILESTREAM).
FACEBOOK.com stores 6.5 (30 with thumbnails and size versions) billions pictures in files system [ 3 ].
Randal’s white paper [ 2 ] reasons it by:
Well, this does not convince me about necessity to store blobs in database but just about the fact that they should not be accessed/streamed externally through T-SQL but rather through Win32.
Other reasons, I did read, also do not look as convincing to me.
What are your reasons to store blobs in database instead of in file system?
[ 1 ]
Ray Barley . Using FILESTREAM to Store BLOBs in the NTFS File System in SQL Server 2008
http://www.mssqltips.com/tip.asp?tip=1489
[ 2 ]
Paul S. Randal
FILESTREAM Storage in SQL Server 2008
http://msdn.microsoft.com/en-us/library/cc949109(SQL.100).aspx
[ 3 ]
James Hamilton’s Blog article. Facebook: Needle in a Haystack: Efficient Storage of Billions of Photos
http://perspectives.mvdirona.com/2008/06/30/FacebookNeedleInAHaystackEfficientStorageOfBillionsOfPhotos.aspx
There can be many advantages to storing such data in a database rather than a filesystem:
Data integrity – you can implement constraints on it
Transaction support
Manageability – backup and restore options
High availability – databases tend to have more sophisticated options for mirroring and clustering than file systems do.
Security – you get the kind of fine-grained security controls that you do not with a filesystem
Accessibility – tables within a database are accessible to all sort of applications for presentation and analysis purposes. Databases can easily be interrogated with SQL statements
Audit – you can record and monitor changes to data
I expect there are many, many other reasons but these are the ones that first came to mind.