Splitting data equaly from one .mdf to several .ndf files

Question

Hi all,
Situation:
We have a db with 1 TB of data in one .mdf file (sql 2012).
For better performance we want to split this file up into 4 equaly big data files on different drives.
1st guess:
Well I thought that's pretty simple, I just add 4 datafiles (.ndf) on different drives, empty my existing .mdf and drop it finaly.
Well the problem with this is, you cannot delete your .mdf file because it holds metadata (catalog) for your db.
Solution:
- I added 3 more datafiles (.ndf) with 250 GB size each, autogrow disabled, on 3 additional drives (no new filegroup)
- DBCC SHRINKFILE (your_logical_mdf_file, EMPTYFILE)
  (this gives you an error because there is not enough diskspace to split the 1TB .mdf file into 3 x 250 GB .ndf files, but it splits your 1 TB file equaly to all your 4 db files)
- shrinked my .mdf file and adjusted filesize and autogrow settings for all 4 db files
Remark:
Just keep in mind that moving 1 TB of data around takes a while and you better do this in a not so busy time...
HTH
acki4711

Answer 1

Neha,
I don't see any advantage of the IO with filegroups.
We don't want to deal with what object should be in what filegroup, (most of the time we maintain 3rd party software/dbs) just want to get better performance by splitting data into more then one db file.
acki4711
You could benefit from performance by splitting data in upto 4 or 8 files and each file on a different drive.
How are the underlying disks configured, do you know? Otherwise, if all of these volumes are carved out of a single lun then there won't be a performance gain that you are looking for. Also, please enable TF 1117 for uniform db file growth once you size
the files to be of equal size.
Note: You may want to test the emptyfile option on your .mdf file, as it may not be straightfoward.
HTH
Hello AlliedDBA,
There is no benefit by splitting database files on different disk drives if your Underlying hardware is RAID 10 or RAID 5 you can achieve performance benefit.Daa to data files are written in Round robin fashion and you dont have any control over it.
Please dont enable any Trace flag.I am not sure what could be solution beacause IMO you anyhow require space
Please mark this reply as the answer or vote as helpful, as appropriate, to make it useful for other readers
Hello Shanky..
Thanks for your feedback, but, I still stand by my suggestion. I see you are opinionating here, so please post some facts to back your claims that 1. No advantage of having multiple files 2. Not sure why your are scared of the term Trace flag but your
statement "IMO anyhow require space" lacks clarity..What is the relationship between space and trace flag??