Store file on file system or as varbinary(MAX) in

Question

I understand that there is a lot of controversy over whether it is bad practice to store files as blob's in a database, but I just want to understand whether this would make sense in my case.

I am creating an ASP.NET application, used internally at a large company, where the users needs to be able to attach files to a 'job' in the system. These files are generally PDF's or Word documents, probably never exceeding a couple of mb.

I am creating a new table like so:

ID (int)
JobID (int)
FileDescription (nvarchar(250))
FileData (varbinary(MAX)

Is the use of varbinary(MAX) here ideal, or should I be storing the path to the file and simply storing the file on the file system somewhere?

Answer 1

There's a really good paper by Microsoft Research called To Blob or Not To Blob.

Their conclusion after a large number of performance tests and analysis is this:

• if your pictures or document are typically below 256K in size, storing them in a database VARBINARY column is more efficient

• if your pictures or document are typically over 1 MB in size, storing them in the filesystem is more efficient (and with SQL Server 2008's FILESTREAM attribute, they're still under transactional control and part of the database)

• in between those two, it's a bit of a toss-up depending on your use

If you decide to put your pictures into a SQL Server table, I would strongly recommend using a separate table for storing those pictures - do not store the employee foto in the employee table - keep them in a separate table. That way, the Employee table can stay lean and mean and very efficient, assuming you don't always need to select the employee foto, too, as part of your queries.

For filegroups, check out Files and Filegroup Architecture for an intro. Basically, you would either create your database with a separate filegroup for large data structures right from the beginning, or add an additional filegroup later. Let's call it LARGE_DATA.

Now, whenever you have a new table to create which needs to store VARCHAR(MAX) or VARBINARY(MAX) columns, you can specify this file group for the large data:

 CREATE TABLE dbo.YourTable
     (....... define the fields here ......)
     ON Data                   -- the basic "Data" filegroup for the regular data
     TEXTIMAGE_ON LARGE_DATA   -- the filegroup for large chunks of data

Check out the MSDN intro on filegroups, and play around with it!