Filestream datatype - what it is?
My question is have you looked into the CTP4 Books online for SQL 2008?
This is new to SQL Server arena, the FileStream data type which allows large binary data to be stored in the file system and yet remain an integral part of the database with transactional consistency. It means the consistency of transactional is taken care and performance gain will be addressed provided you are using it for sensible causes.
So the new applications you are developing or want to modify with this new use of storage type “VARBINARY(MAX) FILESTREAM” to define table columns and store large binary data as files in the file system instead of as a SQL BLOB. For the performance and accessiblity you can use T-SQL SELECT/INSERT/UPDATE/DELETE statements to query and modify FILESTREAM data and You store the documents in SQL Server!".
As of now this is not documented enough on the SQL 2008 CTP books online, more on this can be found with upcoming CTP releases.