Hello I just read http://www.sql-server-performance.com/ac_filegroup_performance.asp and http://www.microsoft.com/technet/prodtechnol/sql/bestpractice/storage-top-10.mspx I have some questions about creating multiple data files and filegroups when you have multiple disks. Today we have 14 disks in a SAN. We only have one small database (20GB). We place the transaction log on 2 disks (raid 1) we place the system databases/tempdb and transaction log backup on 2 disks (raid 1) we place the data files on 10 disks (raid 10) We are going to extend our SAN with 6 more disks. I am thinking of having two more for the data and then separate the system db/tempdb/t.log backup on 6 disks instead of 2. After that we will have a setup like 2 disks for tempdb (raid 1) 2 disks for system databases (raid 1) 2 disks for trasaction log backup (raid 1) 2 disks for transaction log (raid 1) 12 disks for user database (raid 10) Now to my questions. I read some recommendations that quote:It is recommended to have .25 to 1 data files (per filegroup) for each CPU on the host server. This is especially true for TEMPDB where the recommendation is 1 data file per CPU. Does this mean that if we have 4 CPUs, that I will create 4 data files for the temp-db? But we would still only have 2 disks. What is happening in the background here? Why is it better to have more data files? Then in the other article (from sql-server-performance), i read this: quote:If you have several physical disk arrays, try to create as many files as there are physical disk arrays so that you have one file per disk array.What does that mean in my case? And another one from the same article quote:For heavily accessed tables, place these tables in one filegroup and place the table's indexes in a different filegroup on different physical disk arrays.If we today use 10 disks (raid 10) for booth the data and the indexes, how can i measure how many disks that is needed for the indexes? And the last question. Do I just create an extra datafile and then it will be used by SQL-Server, or do I need to specify it in any more way? Some more information about how multiple data files is appreciated.