Configure log file to be on a particular disk of a RAID array

Question

I'm looking at a server which has RAID1+0 array and a RAID 5 array. The RAID 1+0 is used for system files and the RAID 5 array is used for SQL server database and log files.

The RAID 5 array is made up of 6 72GB SAS drives. In the HP array configuration utility they are each seen as something like "72GB SAS Dtive at Port 1l:Box 1: Bay 3". In windows they are seen as one partition named D.

So I have heard it is a good idea to split the tempdb over multiple files for each CPU and physical disk. I have 16 CPUs and 6 disks in the RAID 5 array. So I want to create 6 data files for the tempdb.

Now when I go to alter the tempdb to add a new data file I can select the D drive... but how do I configure it so that each of the six files are placed on a separate physical disk on the RAID array?

Answer 1

Hi Jimmy,

When talking about separation of data files, the word disk can be interchanged with LUN's. It sounds though as if you are only using a single LUN i.e. presenting your entire RAID 5 array as a single partition.

Do you have 16 CPU's or 16 cores, for example 4 quad core CPU's? You should only really look to create a separate data file for each 'true' CPU in my opinion.

I suggest you read the following articles regarding the tempdb database before going ahead with any changes. Paying particular attention "Should I create multiple tempdb database files?".

All about the tempdb database

Answer 2

I think you might need to do a bit of reading on RAID. http://en.wikipedia.org/wiki/RAID

Using 5, your data is automatically striped over the disks in your array. You cannot choose on which disk it goes.

http://msdn.microsoft.com/en-us/library/ms190764.aspx

I don't remember reading any recommendations that you should put each of these files on a separate disk either.