SQL 2012 :: DBCC Shrinkfile Empty File Not Distributing Data Evenly In Primary File Group With Multiple Files

Why shrinkfile empty file does not redistribute data evenly in the primary file group with multiple files:

Please run the script attached to see what the end result is.

This is what I set up last night on my test machine.

1) Create database [FGTest] size 200MB
2) Create table called TEST on primary
3) Insert 40MB of data into test
4) Create another file group called temp in primary size 200MB
5) Shrinkfile('FGTest',emptyfile) so that all data is transfered from FGTest into temp file group.
6) Add another 2 files called DATA2 and DATA3. Both are 200MB.
7) We now have 3 empty files that I want data distributed evenly on. FGTest, DATA2 & DATA3
8) Shrinkfile('temp',emptyfile) to move all the data from temp over the 3 file groups evenly

I would expect at this stage to have the following:

FGTest = 13MB,
DATA2 = 13MB,
DATA3 = 13MB

(40MB of data over 3 files should be about 13 MBish in each file)

What I actually end up with is this:

FGTest = 20MB
DATA1 = 10MB
DATA2 = 10MB

It looks as though SQL Server is allocating 50% of all data to the original file and then 50% evenly over
the remaining files in PRIMARY.