Nick Grattan's Blog

About Microsoft SharePoint, .NET, Natural Language Processing and Machine Learning

Storing BLOBs Externally in SharePoint 2007

with 2 comments

Documents in SharePoint Document Libraries are stored in the SQL Server database. In most situations this works well – backing up the SQL Server content database backs up all the documents in a consistent way.

However, for storing Binary Large Objects (BLOBs) may be inefficient and costly. It may be more efficient to store such BLOBs in the file system and then link these files to SharePoint Document Libraries.

This can now be done through the ISPExternalBinaryProvider interface. Prior to SharePoint 2007 SP1 this component was available as a hot fix, but is now included mainstream.

The interface is documented here:

Written by Nick Grattan

January 17, 2008 at 12:54 pm

2 Responses

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  1. Hi Nick,
    there are some serious downsides with the external storage.
    (see my blog:
    – With the current version only the SPFarm is supported. Meaning ALL content will be stored externally
    – After you have implemented an external storage provider, all new documents will be stored in this place. To move old documents, you could do a Backup/Retore of your content.
    – Changing a document will create a new blob and not disposing the old one. You have to do this manually (you can implement garbage collection)!


    René Hézser

    October 1, 2008 at 9:56 am

  2. René, thanks for your comments – very useful, Regards, Nick

    Nick Grattan

    October 1, 2008 at 12:18 pm

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